chore(deps): update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/tests.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
       - name: Setup PHP
         run: |
           sudo update-alternatives --set php /usr/bin/php7.4