Fix the typo on actions/checkout@v4

Author: cuviper

Diff for: .github/workflows/ci.yaml

@@ -37,7 +37,7 @@ jobs:
     name: Format
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v4
       - uses: dtolnay/[email protected]
         with:
           components: rustfmt