chore(deps): update dependency protobuf to v3.19.3 (googleapis#1150)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [protobuf](https://developers.google.com/protocol-buffers/) | `==3.19.1` -> `==3.19.3` | [![age](https://badges.renovateapi.com/packages/pypi/protobuf/3.19.3/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/pypi/protobuf/3.19.3/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/pypi/protobuf/3.19.3/compatibility-slim/3.19.1)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/pypi/protobuf/3.19.3/confidence-slim/3.19.1)](https://docs.renovatebot.com/merge-confidence/) |

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requirements.txt

@@ -3,7 +3,7 @@ google-api-core==2.1.1
 googleapis-common-protos==1.54.0
 jinja2==3.0.3
 MarkupSafe==2.0.1
-protobuf==3.19.1
+protobuf==3.19.3
 pypandoc==1.6.4
 PyYAML==6.0
 dataclasses==0.6  # TODO(busunkim) remove when 3.6 support is dropped