message: Fix typo in test_common/utility.h
  Fixes a typo from
  Risk Level: Low
diff: @@ -445,7 +445,7 @@ public:
  ProtobufMessage::getStrictValidationVisitor());
  }
  - static void jsonConvert(const ProtobufWkt::Message& source, Protobuf::Message& dest) {
  + static void jsonConvert(const Protobuf::Message& source, Protobuf::Message& dest) {
  // Explicit round-tripping to support conversions inside tests between arbitrary messages as a
  // convenience.
  ProtobufWkt::Struct tmp;
  