Have tests podspecs make only the ObjC plugin

src/objective-c/generated_libraries/RemoteTestClient/RemoteTest.podspec

@@ -9,8 +9,7 @@ Pod::Spec.new do |s|
   # Run protoc with the Objective-C and gRPC plugins to generate protocol messages and gRPC clients.
   s.prepare_command = <<-CMD
     cd ../../../..
-    # TODO(jcanizales): Make only Objective-C plugin.
-    make plugins
+    make grpc_objective_c_plugin
     cd -
     protoc --plugin=protoc-gen-grpc=../../../../bins/opt/grpc_objective_c_plugin --objc_out=. --grpc_out=. *.proto
   CMD

src/objective-c/generated_libraries/RouteGuideClient/RouteGuide.podspec

@@ -9,8 +9,7 @@ Pod::Spec.new do |s|
   # Run protoc with the Objective-C and gRPC plugins to generate protocol messages and gRPC clients.
   s.prepare_command = <<-CMD
     cd ../../../..
-    # TODO(jcanizales): Make only Objective-C plugin.
-    make plugins
+    make grpc_objective_c_plugin
     cd -
     protoc --plugin=protoc-gen-grpc=../../../../bins/opt/grpc_objective_c_plugin --objc_out=. --grpc_out=. *.proto
   CMD