fix(pubsub/pstest): update maxMessageRetentionDuration to be 31 days#8199

hongalex merged 2 commits intogoogleapis:maingoogleapis/google-cloud-go:mainfrom

xvzf:fix/update-max-ps-topic-retentionxvzf/google-cloud-go:fix/update-max-ps-topic-retentionCopy head branch name to clipboard