nix: fix nix environment for GHC 9.4

- Bumped nixpkgs, so that's a true GHC 9.4.1 and not 9.4.0, which was
  failing in cabal which because it was detecting <=9.4.1.
- Use the "default" GHC environment for tooling in the shell. Hence it
  rebuilds less.

Author: guibou

flake.lock

@@ -282,16 +282,16 @@
             hpkgs.ghc
             pkgs.cabal-install
             # @guibou: I'm not sure hie-bios is needed
-            ghcDefault.hie-bios
+            pkgs.haskellPackages.hie-bios
             # Dependencies needed to build some parts of hackage
             gmp zlib ncurses
             # Changelog tooling
-            (gen-hls-changelogs ghcDefault)
+            (gen-hls-changelogs pkgs.haskellPackages)
             # For the documentation
             pythonWithPackages
             # @guibou: I'm not sure this is needed.
             hlint
-            ghcDefault.opentelemetry-extra
+            pkgs.haskellPackages.opentelemetry-extra
             capstone tracy
             # ormolu
             # stylish-haskell