Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - name: Mount bazel cache
       uses: actions/cache@v3