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

mojo/public/c/tests/bindings/validation_unittest.cc

Index: mojo/public/c/tests/bindings/validation_unittest.cc
diff --git a/mojo/public/c/tests/bindings/validation_unittest.cc b/mojo/public/c/tests/bindings/validation_unittest.cc
index 1d1ee431ebc5e8a7ef4cb799aa95206da3912ae3..9dbc5c3d93326155a6d4ebf1228d4fc81fb5fd92 100644
--- a/mojo/public/c/tests/bindings/validation_unittest.cc
+++ b/mojo/public/c/tests/bindings/validation_unittest.cc
@@ -14,11 +14,11 @@
 #include <functional>
 #include <string>
 
+#include "gtest/gtest.h"
 #include "mojo/public/cpp/bindings/tests/validation_util.h"
 #include "mojo/public/cpp/system/macros.h"
 #include "mojo/public/cpp/test_support/test_support.h"
 #include "mojo/public/interfaces/bindings/tests/validation_test_interfaces.mojom-c.h"
-#include "testing/gtest/include/gtest/gtest.h"
 
 using mojo::test::EnumerateSourceRootRelativeDirectory;