CI: Bump checkout to v4

Author: nitinprakash96

.github/workflows/checks.yml

@@ -18,7 +18,7 @@ jobs:
       run: |
         sudo apt install -y fd-find
 
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - name: git fetch
       run: git fetch origin main:main
@@ -68,7 +68,7 @@ jobs:
         which stylish-haskell
         stylish-haskell --version
 
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - name: "Run `stylish-haskell`"
       run: |

.github/workflows/haskell.yml

@@ -48,7 +48,7 @@ jobs:
         echo "PATH = $PATH"
         echo "LLVM_CONFIG = $LLVM_CONFIG"
 
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - name: "Configure cabal.project.local"
       run: |