fix(generator): filter out empty services from api.services

Author: shivanee-p

core/generator/gapic-generator-typescript/typescript/src/schema/api.ts

@@ -207,7 +207,14 @@ export class API {
       .filter(proto => proto.fileToGenerate)
       .reduce((retval, proto) => {
         retval.push(
-          ...Object.keys(proto.services).map(name => proto.services[name]),
+          ...Object.keys(proto.services)
+            .map(name => proto.services[name])
+            .filter(
+              service =>
+                (service.method && service.method.length > 0) ||
+                service.IAMPolicyMixin > 0 ||
+                service.LocationMixin > 0,
+            ),
         );
         return retval;
       }, [] as ServiceDescriptorProto[])