Update actions/checkout to the latest version

Author: willnet

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
             continue-on-error: true
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v5
 
     - name: Set RABL_GEM environment variable
       run: echo "RABL_GEM=${{ matrix.rabl-gem }}" >> $GITHUB_ENV