Remove more references to GAE (#2894)

These are old/pointless now that we've migrated to GKE. Note that this
doesn't update anything in the docs/ folder, as that's a much larger
project that should be done on its own.

build.gradle

@@ -84,10 +84,10 @@ tasks.build.dependsOn(tasks.checkLicense)
 // Paths to main and test sources.
 ext.projectRootDir = "${rootDir}"
 
-// Tasks to deploy/stage all App Engine services
+// Tasks to deploy/stage all services
 task deploy {
   group = 'deployment'
-  description = 'Deploys all services to App Engine.'
+  description = 'Deploys all services.'
 }
 
 task stage {