chore: bump com.google.protobuf:protoc in /java/gradle

Bumps [com.google.protobuf:protoc](https://github.com/protocolbuffers/protobuf) from 3.25.5 to 3.25.6.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/main/protobuf_release.bzl)
- [Commits](protocolbuffers/protobuf@v3.25.5...v3.25.6)

---
updated-dependencies:
- dependency-name: com.google.protobuf:protoc
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

java/gradle/build.gradle

@@ -42,7 +42,7 @@ sourceSets {
 
 protobuf {
   protoc {
-    artifact = "com.google.protobuf:protoc:3.25.5"
+    artifact = "com.google.protobuf:protoc:3.25.6"
   }
   plugins {
     grpc {