build(fix): bump-up protobufVersion to 3.21.12 (latest)

[laysakura]

Problem

The following command fails in M1 Mac (osx-aarch_64).

./gradlew :rpc:generateProto  # called from `./gradlew test`, for example

> Task :rpc:generateProto FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':rpc:generateProto'.
> Could not resolve all files for configuration ':rpc:protobufToolsLocator_protoc'.
   > Could not find protoc-3.20.3-osx-aarch_64.exe (com.google.protobuf:protoc:3.20.3).
     Searched in the following locations:
         https://repo.maven.apache.org/maven2/com/google/protobuf/protoc/3.20.3/protoc-3.20.3-osx-aarch_64.exe

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

Deprecated Gradle features were used in this build, making it incompatible with Gradle 8.0.
Use '--warning-mode all' to show the individual deprecation warnings.
See https://docs.gradle.org/7.0.2/userguide/command_line_interface.html#sec:command_line_warnings

BUILD FAILED in 646ms
3 actionable tasks: 1 executed, 2 up-to-date

This is because the version 3.20.3 does not include protoc binary for osx-aarch_64 in the maven repository, while 3.21.12 does.

• https://repo1.maven.org/maven2/com/google/protobuf/protoc/3.20.3/
• https://repo1.maven.org/maven2/com/google/protobuf/protoc/3.21.12/

Refs: protocolbuffers/protobuf#8062

What I did

Bump up protobufVersion from 3.20.3 to 3.21.12 (latest).

I'm not sure...

The command:

./gradlew :rpc:generateProto

leads to the following diffs. Currently I don't commit the diffs but I will if necessary.

rpc-generateProto.diff.txt

[laysakura]

close this fork version in favor of: #760