Update actions/checkout action to v5 [skip ci]

Author: leomp12

.github/workflows/calibreapp-image-actions.yml

@@ -16,7 +16,7 @@ jobs:
     name: calibreapp/image-actions
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - name: Compress images
         uses: calibreapp/image-actions@main
         with: