Bump protobufVersion from 3.11.4 to 3.12.0

Bumps `protobufVersion` from 3.11.4 to 3.12.0.

Updates `protoc` from 3.11.4 to 3.12.0
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/master/generate_changelog.py)
- [Commits](protocolbuffers/protobuf@v3.11.4...v3.12.0)

Updates `protobuf-java` from 3.11.4 to 3.12.0
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/master/generate_changelog.py)
- [Commits](protocolbuffers/protobuf@v3.11.4...v3.12.0)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

build.gradle

@@ -12,7 +12,7 @@ allprojects {
 
 ext {
     grpcVersion = '1.29.0'
-    protobufVersion = '3.11.4'
+    protobufVersion = '3.12.0'
 }
 
 subprojects {