Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/ci.yml

@@ -28,7 +28,7 @@ jobs:
           - 5432:5432
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0 # fetch all history
 
@@ -76,7 +76,7 @@ jobs:
     runs-on: ubuntu-22.04
     if: startsWith(github.ref, 'refs/tags/')
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - uses: actions/setup-python@v5
       with: