avro

Bump grpc.version from 1.37.1 to 1.38.0 in /lang/java (#1229)

Bumps `grpc.version` from 1.37.1 to 1.38.0.

Updates `grpc-core` from 1.37.1 to 1.38.0
- [Release notes](https://github.com/grpc/grpc-java/releases)
- [Commits](https://github.com/grpc/grpc-java/compare/v1.37.1...v1.38.0)

Updates `grpc-stub` from 1.37.1 to 1.38.0
- [Release notes](https://github.com/grpc/grpc-java/releases)
- [Commits](https://github.com/grpc/grpc-java/compare/v1.37.1...v1.38.0)

Updates `grpc-netty` from 1.37.1 to 1.38.0
- [Release notes](https://github.com/grpc/grpc-java/releases)
- [Commits](https://github.com/grpc/grpc-java/compare/v1.37.1...v1.38.0)

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