GN: Remove "outputs" parameter for java_cpp_enum()

sync/android/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/config.gni")
 import("//build/config/android/rules.gni")
 
 android_library("sync_java") {
   deps = [
     "//base:base_java",
@@ skipping 19 matching lines @@
     "//third_party/jsr-305:jsr_305_javalib",
   ]
   DEPRECATED_java_in_dir = "javatests/src"
 }
 
 # GYP: //sync/sync_android.gypi:model_type_java
 java_cpp_enum("java_enums") {
   sources = [
     "//sync/internal_api/public/base/model_type.h",
   ]
-  outputs = [
-    "org/chromium/sync/ModelType.java",
-  ]
 }
 
 generate_jni("jni_headers") {
   sources = [
     "java/src/org/chromium/sync/ModelTypeHelper.java",
   ]
   jni_package = "syncer"
 }