chore: use java helper for templates (#114)

Author: chingor13

synth.py

@@ -49,8 +49,6 @@
     java.format_code(f'grpc-google-cloud-{service}-{version}/src')
     java.format_code(f'proto-google-cloud-{service}-{version}/src')
 
-common_templates = gcp.CommonTemplates()
-templates = common_templates.java_library()
-s.copy(templates, excludes=[
+java.common_templates(excludes=[
     'README.md'
-])
+])