Make tests use test metadata (#2836)

This is a continuation of #2762

Co-authored-by: penmetsaa <penmetsaa@google.com>

cpp/src/phonenumbers/test_metadata.cc

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#include "phonenumbers/metadata.h"
+#include "phonenumbers/test_metadata.h"
 
 namespace i18n {
 namespace phonenumbers {