build(deps): bump com.google.errorprone:javac

Bumps [com.google.errorprone:javac](https://github.com/google/error-prone-javac) from 9+181-r4173-1 to 1.8.0-u20.
- [Commits](https://github.com/google/error-prone-javac/commits)

---
updated-dependencies:
- dependency-name: com.google.errorprone:javac
  dependency-type: direct:production
...

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

gradle/libs.versions.toml

@@ -65,7 +65,7 @@ autoServiceProcessor = { module = "com.google.auto.service:auto-service", versio
 
 errorprone = { module = "com.google.errorprone:error_prone_core", version.ref = "errorprone" }
 errorproneAnnotations = { module = "com.google.errorprone:error_prone_annotations", version.ref = "errorprone" }
-errorproneJavac = { module = "com.google.errorprone:javac", version = "9+181-r4173-1" }
+errorproneJavac = { module = "com.google.errorprone:javac", version = "1+" }
 
 [bundles]
 grpc    = [ "grpcCore", "grpcNetty", "grpcProtobuf", "grpcStub", "grpcGrpclb" ]