Fix build on clang-r522817

hardware/interfaces/automotive/can/1.0/tools/libprotocan/MessageInjector.cpp:44:8: error: no member named 'lock_guard' in namespace 'std'
   44 |   std::lock_guard<std::mutex> lock(mMessagesGuard);
      |   ~~~~~^

Bug: 322868540
Test: presubmit
Change-Id: I45cd6a8420e508a37e2b6da456933c036493e15e