CI bumbed to actions/checkout@v4

Author: tonyday567

.github/workflows/haskell-ci.yml

@@ -38,7 +38,7 @@ jobs:
             name: docspec
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Set up GHC ${{ matrix.ghc-version }}
         uses: haskell-actions/setup@v2