fix(deps): update dependency google/cloud-spanner to v2#2168

bshaffer merged 1 commit intoGoogleCloudPlatform:mainGoogleCloudPlatform/php-docs-samples:mainfrom

renovate-bot:renovate/grpc-google-cloud-spanner-2.xrenovate-bot/php-docs-samples:renovate/grpc-google-cloud-spanner-2.xCopy head branch name to clipboard