;ci: windows: try using ghc 8.8.4 (& default stack.yaml)

It's better to use a stack.yaml file than just a resolver, since the
former declares extra deps we may need from time to time.
Try with ghc 8.8.4, hopefully it's good enough on windows.

.github/workflows/windows.yml

@@ -128,13 +128,14 @@ jobs:
         which ./stack
         ./stack --version
 
-    # resolver lts-15.3 to avoid GHC 8.8.3 access violation, https://gitlab.haskell.org/ghc/ghc/issues/17926:
+    # must avoid GHC versions broken on windows such as 8.8.3 with https://gitlab.haskell.org/ghc/ghc/issues/17926
+    # current default stack.yaml uses GHC 8.8.4 which hopefully is ok
 
     - name: Install GHC
       # if: steps.stack-programs-dir.outputs.cache-hit != 'true'
       # set PATH=C:\Users\runneradmin\AppData\Local\Programs\stack\local\bin;%PATH%
       run: |
-        ./stack --resolver=lts-15.3 --no-terminal setup --install-ghc
+        ./stack --no-terminal setup --install-ghc
 
     # - name: Install shelltestrunner
     ## - export PATH=~/.local/bin:$PATH
@@ -143,11 +144,11 @@ jobs:
 
     - name: Install haskell deps
       run: |
-        ./stack --resolver=lts-15.3 --no-terminal build --only-dependencies
+        ./stack --no-terminal build --only-dependencies
 
     - name: Build all hledger modules warning free, optimised and minimised
       run: |
-        ./stack --resolver=lts-15.3 --no-terminal install --force-dirty --ghc-options=-fforce-recomp --ghc-options=-Werror
+        ./stack --no-terminal install --force-dirty --ghc-options=-fforce-recomp --ghc-options=-Werror
       # --ghc-options=-split-sections doesn't work on windows, "too many sections"
       # --pedantic