Remove GYP annotations from third_party GN files.

third_party/errorprone/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/rules.gni")
 
-# GYP: //third_party/errorprone/errorprone.gyp:error_prone_annotation_jar
 java_prebuilt("error_prone_annotation_java") {
   jar_path = "lib/error_prone_annotation-2.0.5.jar"
 }
 
-# GYP: //third_party/errorprone/errorprone.gyp:error_prone_annotations_jar
 java_prebuilt("error_prone_annotations_java") {
   jar_path = "lib/error_prone_annotations-2.0.5.jar"
 }
 
-# GYP: //third_party/errorprone/errorprone.gyp:javac_jar
 java_prebuilt("javac_java") {
   jar_path = "lib/javac-1.9.0-dev-r2644-1.jar"
 }
 
-# GYP: //third_party/errorprone/errorprone.gyp:dataflow_jar
 java_prebuilt("dataflow_java") {
   jar_path = "lib/dataflow-1.8.10.jar"
 }
 
-# GYP: //third_party/errorprone/errorprone.gyp:javacutil_jar
 java_prebuilt("javacutil_java") {
   jar_path = "lib/javacutil-1.8.10.jar"
 }
 
-# GYP: //third_party/errorprone/errorprone.gyp:chromium_errorprone
 java_prebuilt("chromium_errorprone") {
   jar_path = "lib/error_prone_core-2.0.5.jar"
   deps = [
     ":dataflow_java",
     ":error_prone_annotation_java",
     ":error_prone_annotations_java",
     ":javac_java",
     ":javacutil_java",
     "//third_party/findbugs:format_string_java",
   ]
   main_class = "com.google.errorprone.ErrorProneCompiler"
 
   # TODO(mikecase): Remove this extra arg when the bots are on jdk8 or higher.
   bootclasspath =
       "$root_build_dir/lib.java/third_party/errorprone/javac_java.jar"
 }