build old docs with their release notes (#6128)

In light of #6127, I kept wondering why rebuilding 1.1.1 would fail. The
problem addressed by #6127 is that we tried to rebuild it, which we
shouldn't, but the reason I noticed it is because the build failed, and
there is no good reason for the 1.1.1 docs to not build anymore. Looking
at the logs confused me even more as it failed with (elided):

```
docs/source/support/new-assistant.rst:
WARNING: document isn't included in any toctree
```

and that change happened _after_ 1.1.1. So I went back to the code, and
discovered I somehow had gotten confused as I changed the approach
mid-way through editing the file. If we're overwriting the
`release-notes.html` file post-build, which we are now doing (and is the
reason for ignoring it when checking checksums), then we should not be
touching the `release-notes.rst` file pre-build.

CHANGELOG_BEGIN
CHANGELOG_END

ci/cron/src/Main.hs

@@ -110,7 +110,6 @@ to_v s = case Split.splitOn "-" s of
 build_docs_folder :: String -> [GitHubVersion] -> String -> IO String
 build_docs_folder path versions current = do
     restore_sha $ do
-        latest_release_notes_sha <- init <$> shell "git log -n1 --format=%H HEAD -- LATEST"
         let old = path </> "old"
         let new = path </> "new"
         shell_ $ "mkdir -p " <> new
@@ -148,7 +147,7 @@ build_docs_folder path versions current = do
                     return $ Just (gh_version, False)
                 else do
                     putStrLn "  Not found. Building..."
-                    build version new latest_release_notes_sha
+                    build version new
                     return $ Just (gh_version, True)
             else if old_version_exists
             then do
@@ -164,11 +163,11 @@ build_docs_folder path versions current = do
                     return $ Just (gh_version, False)
                 else do
                     putStrLn "  Check failed. Rebuilding..."
-                    build version new latest_release_notes_sha
+                    build version new
                     return $ Just (gh_version, True)
             else do
                 putStrLn "  Not found. Building..."
-                build version new latest_release_notes_sha
+                build version new
                 return $ Just (gh_version, True))
         putStrLn $ "Copying current (" <> current <> ") to top-level..."
         copy (new </> current </> "*") (new <> "/")
@@ -176,6 +175,15 @@ build_docs_folder path versions current = do
         let (releases, snapshots) = List.partition (not . prerelease . fst) documented_versions
         create_versions_json (map fst releases) (new </> "versions.json")
         create_versions_json (map fst snapshots) (new </> "snapshots.json")
+        -- Starting after 0.13.54, we have changed the way in which we trigger
+        -- releases. Rather than releasing the current commit by changing the
+        -- VERSION file, we now mark an existing commit as the source code for
+        -- a release by changing the LATEST file. This raises the question of
+        -- the release notes: as we tag a commit from the past, and keep the
+        -- changelog outside of the worktree (in commit messages), that means
+        -- that commit cannot contain its own release notes. We have decided to
+        -- resolve that conundrum by always including the release notes from
+        -- the most recent release in all releases.
         case filter snd documented_versions of
           ((newly_built,_):_) -> do
               putStrLn $ "Copying release notes from " <> name newly_built <> " to all other versions..."
@@ -204,7 +212,7 @@ build_docs_folder path versions current = do
                 _ -> return False
         copy from to = do
             shell_ $ "cp -r " <> from <> " " <> to
-        build version path latest_sha = do
+        build version path = do
             shell_ $ "git checkout v" <> version
             -- Maven does not accept http connections anymore; this patches the
             -- scala rules for Bazel to use https instead. This is not needed
@@ -213,24 +221,8 @@ build_docs_folder path versions current = do
             then do
                 shell_ "git -c user.name=CI -c user.email=CI@example.com cherry-pick 0c4f9d7f92c4f2f7e2a75a0d85db02e20cbb497b"
                 build_helper version path
-            else if to_v version < to_v "0.13.55"
-            then do
-                build_helper version path
-            -- Starting after 0.13.54, we have changed the way in which we
-            -- trigger releases. Rather than releasing the current commit by
-            -- changing the VERSION file, we now mark an existing commit as the
-            -- source code for a release by changing the LATEST file. This
-            -- raises the question of the release notes: as we tag a commit
-            -- from the past, and keep the changelog outside of the worktree
-            -- (in commit messages), that means that commit cannot contain its
-            -- own release notes. We have decided to resolve that conundrum by
-            -- always including the release notes from the most recent release
-            -- in all releases.
             else do
-                Control.Exception.bracket_
-                    (shell_ $ "git checkout " <> latest_sha <> " -- docs/source/support/release-notes.rst")
-                    (shell_ "git reset --hard")
-                    (build_helper version path)
+                build_helper version path
         build_helper version path = do
             robustly_download_nix_packages version
             shell_ $ "DAML_SDK_RELEASE_VERSION=" <> version <> " bazel build //docs:docs"