ledger: remove old version 2.6.3

Version 2.6.3 was released > 5 years ago and has been marked as broken for some
time. It is time to remove it.

This also documents why ledger3 cannot yet build with boost >= 1.67

pkgs/applications/office/ledger/2.6.3.nix

@@ -1,41 +0,0 @@
-{ stdenv, fetchurl, emacs, gmp, pcre, expat }:
-
-stdenv.mkDerivation rec {
-  name = "ledger2-2.6.3";
-
-  src = fetchurl {
-    url = "https://github.com/downloads/ledger/ledger/${name}.tar.gz";
-    sha256 = "05zpnypcwgck7lwk00pbdlcwa347xsqifxh4zsbbn01m98bx1v5k";
-  };
-
-  buildInputs = [ emacs gmp pcre expat ];
-
-  configureFlags = [
-    "CPPFLAGS=-DNDEBUG"
-    "CFLAGS=-O3"
-    "CXXFLAGS=-O3"
-  ];
-
-  doCheck = true;
-
-  # Patchelf breaks the hard-coded rpath to ledger's libamounts.0.so and
-  # libledger-2.6.3.so. Fortunately, libtool chooses proper rpaths to
-  # begin with, so we can just disable patchelf to avoid the issue.
-  dontPatchELF = true;
-
-  meta = {
-    homepage = https://ledger-cli.org/;
-    description = "A double-entry accounting system with a command-line reporting interface";
-    license = "BSD";
-
-    longDescription = ''
-      Ledger is a powerful, double-entry accounting system that is accessed
-      from the UNIX command-line. This may put off some users, as there is
-      no flashy UI, but for those who want unparalleled reporting access to
-      their data, there really is no alternative.
-    '';
-
-    platforms = stdenv.lib.platforms.all;
-    broken = true; # https://hydra.nixos.org/build/59124559/nixlog/1
-  };
-}

pkgs/top-level/all-packages.nix

@@ -20228,11 +20228,12 @@ in
 
   linuxband = callPackage ../applications/audio/linuxband { };
 
-  ledger2 = callPackage ../applications/office/ledger/2.6.3.nix { };
+  ledger = callPackage ../applications/office/ledger {
-  ledger3 = callPackage ../applications/office/ledger {
+    # Boost >= 1.67 changed the name of boost python; ledger's cmake build needs
+    # an update to find it:
+    # https://www.boost.org/doc/libs/1_68_0/libs/python/doc/html/rn.html
     boost = boost15x;
   };
-  ledger = ledger3;
 
   ledger-autosync = callPackage  ../applications/office/ledger-autosync { };