chore(deps): update actions/checkout action to v6 (#637)

Author: renovate-bot

.github/workflows/release.yml

@@ -10,7 +10,7 @@ jobs:
     name: Run google-cloud-php tests
     if: github.event.pull_request.user.login == 'release-please[bot]'
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Clone googleapis/google-cloud-php
       uses: actions/checkout@master
       with:

.github/workflows/tests.yml

@@ -26,7 +26,7 @@ jobs:
                     composerflags: "--prefer-lowest"
         name: "PHP ${{ matrix.php }} Unit Test ${{ matrix.extensions }}${{ matrix.composerflags }}"
         steps:
-            - uses: actions/checkout@v5
+            - uses: actions/checkout@v6
             - name: Setup PHP
               uses: shivammathur/setup-php@v2
               with: