Update checkout actions

Author: rvermeulen

.github/workflows/post-release.yml

@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           ref: ${{ github.event.inputs.ref }}
       - name: Install Python