Update actions/checkout action to v6 (#37782)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

.github/workflows/test-migrations.yml

@@ -72,7 +72,7 @@ jobs:
       BUNDLE_RETRY: 3
 
     steps:
-      - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
 
       - name: Set up Ruby environment
         uses: ./.github/actions/setup-ruby