Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/semgrep.yml

@@ -21,5 +21,5 @@ jobs:
       image: returntocorp/semgrep
     if: (github.actor != 'dependabot[bot]')
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - run: semgrep ci