scala example: no longer specify 'grpc' option statically (#290)

The plugin for scala adds "grpc" into the options based on if there
are services present, and no longer needs to be specified in the config
like this.  This change fixes 'bazel run //:gazelle` for the examples.

Author: pcj

.bazelrc

@@ -1 +1,3 @@
 build:bazelci --deleted_packages=docs
+# workaround for scala
+build --incompatible_java_common_parameters=false

example/BUILD.bazel

@@ -45,7 +45,6 @@
 
 ## Scala ##
 # gazelle:proto_plugin scala implementation scalapb:scalapb:protoc-gen-scala
-# gazelle:proto_plugin scala option grpc
 # gazelle:proto_plugin scala deps @com_google_protobuf//:protobuf_java
 # gazelle:proto_plugin scala deps @maven_scala//:com_thesamet_scalapb_lenses_2_12
 # gazelle:proto_plugin scala deps @maven_scala//:com_thesamet_scalapb_scalapb_runtime_2_12

example/routeguide/BUILD.bazel

@@ -282,7 +282,6 @@ grpc_scala_library(
 
 proto_compile(
     name = "routeguide_scala_compile",
-    options = {"@build_stack_rules_proto//plugin/scalapb/scalapb:protoc-gen-scala": ["grpc"]},
     outputs = [
         "routeguide_scala.srcjar",
         "routeguide_akka_grpc.srcjar",