Bump Windows/Mac CI to latest 4 major GHCs

Author: andreasabel

.github/workflows/haskell.yml

@@ -15,7 +15,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ghc: ['9.8', '9.6', '9.4']
+        ghc: ['9.12', '9.10', '9.8', '9.6']
         os: [ubuntu-latest, macOS-latest, windows-latest]
     steps:
     - uses: actions/checkout@v4