This PR migrates from autosynth to [owl bot](https://github.com/googleapis/repo-automation-bots/tree/master/packages/owl-bot).  owl bot will save time for maintainers as it will automatically open PRs when there are updates in [googleapis-gen](https://github.com/googleapis/googleapis-gen/tree/master/google) without requiring maintainers to run `synthtool` to build the client from protos. Additionally, similar to autosynth, PRs will be automatically opened when there are template updates.

gcr.io/repo-automation-bots/owlbot-python:latest@sha256:4c981a6b6f2b8914a448d7b3a01688365be03e3ed26dfee399a6aa77fb112eaa

gcr.io/repo-automation-bots/owlbot-python:latest@sha256:3c3a445b3ddc99ccd5d31edc4b4519729635d20693900db32c4f587ed51f7479

gcr.io/repo-automation-bots/owlbot-python:latest@sha256:0856ca711da1fd5ec9d6d7da6c50aa0bbf550fb94acb47b55159a640791987bf

There is [an issue](https://github.com/googleapis/python-firestore/blob/master/owlbot.py#L60) in the `owlbot.py` file added in #352 in that [s.remove_staging_dirs()](https://github.com/googleapis/synthtool/blob/master/synthtool/transforms.py#L309) should only be called once after all the files are copied over.  [get_staging_dirs()](https://github.com/googleapis/synthtool/blob/master/synthtool/transforms.py#L280) will only return staging directories that exist.

Post-Processor: gcr.io/repo-automation-bots/owlbot-python:latest@sha256:c66ba3c8d7bc8566f47df841f98cd0097b28fff0b1864c86f5817f4c8c3e8600

Post-owlbot refresh of PR #272.

…365)

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>