firestore: TestIntegration_DefaultDB failed

This test failed! To configure my behavior, see [the Flaky Bot documentation](https://github.com/googleapis/repo-automation-bots/tree/main/packages/flakybot). If I'm commenting on this issue too often, add the `flakybot: quiet` label and I will stop commenting. --- commit: 24a976e8805e716c8d01ffe9dd7045aefdb8ee69 buildURL: [Build Status](https://source.cloud.google.com/results/invocations/165507ff-b376-4c11-a9ef-380eba62f4dd), [Sponge](http://sponge2/165507ff-b376-4c11-a9ef-380eba62f4dd) status: failed