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

Author: renovate-bot

.github/workflows/ci.yml

@@ -51,7 +51,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
     - name: Checkout repo
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
     - name: Install Ruby ${{ matrix.ruby }}
       uses: ruby/setup-ruby@v1
       with:

.github/workflows/spanner-integration-tests-against-emulator.yaml

@@ -24,7 +24,7 @@ jobs:
           - 9020:9020
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: '3.2'