TrigHLTJetHypoUnitTests: Disable thread-safety checking for gtest tests.

Disable thread-safety checking for unit tests that use googletest. Fixes warnings seen when (disabled by default) warnings about calls to unchecked code are enabled.

Trigger/TrigHypothesis/TrigHLTJetHypoUnitTests/tests/CombinationsGeneratorTest.cxx

 /*
-  Copyright (C) 2002-2023 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
 */
 
+#include "CxxUtils/checker_macros.h"
+ATLAS_NO_CHECK_FILE_THREAD_SAFETY;
+
 #include "gtest/gtest.h"
 #include "TrigHLTJetHypo/../src/CombinationsGenerator.h"
 #include <vector>