mojo/public: Include gtest.h as "gtest/gtest.h", instead of via "absolute" path.

mojo/public/cpp/bindings/tests/constant_unittest.cc

Index: mojo/public/cpp/bindings/tests/constant_unittest.cc
diff --git a/mojo/public/cpp/bindings/tests/constant_unittest.cc b/mojo/public/cpp/bindings/tests/constant_unittest.cc
index f6394f3a644dc9daed18ede0ae4b246146871e37..bb94aac1071ceba125881961c6ab0f76070475ca 100644
--- a/mojo/public/cpp/bindings/tests/constant_unittest.cc
+++ b/mojo/public/cpp/bindings/tests/constant_unittest.cc
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "gtest/gtest.h"
 #include "mojo/public/interfaces/bindings/tests/test_constants.mojom.h"
-#include "testing/gtest/include/gtest/gtest.h"
 
 namespace mojo {
 namespace test {