Remove GYP annotations from third_party GN files.

third_party/errorprone/BUILD.gn

Index: third_party/errorprone/BUILD.gn
diff --git a/third_party/errorprone/BUILD.gn b/third_party/errorprone/BUILD.gn
index 65d86dedc4c37a19d398c54182e4c343e6b5d556..d0c2bacd8f18b4ae1b48d94d0f598af977602ad5 100644
--- a/third_party/errorprone/BUILD.gn
+++ b/third_party/errorprone/BUILD.gn
@@ -4,32 +4,26 @@
 
 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 = [