build(deps): bump grpcio from 1.56.0 to 1.56.2

Bumps [grpcio](https://github.com/grpc/grpc) from 1.56.0 to 1.56.2.
- [Release notes](https://github.com/grpc/grpc/releases)
- [Changelog](https://github.com/grpc/grpc/blob/master/doc/grpc_release_schedule.md)
- [Commits](https://github.com/grpc/grpc/compare/v1.56.0...v1.56.2)

---
updated-dependencies:
- dependency-name: grpcio
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -39,7 +39,7 @@ google-cloud-ndb==2.1.1
 google-cloud-tasks==2.13.2
 googleapis-common-protos==1.59.1
 grpc-google-iam-v1==0.12.6
-grpcio==1.56.0
+grpcio==1.56.2
 gunicorn==21.2.0
 html2text==2020.1.16
 html5lib==1.1