Add thread header inclusion in testCcdbDatabase.cxx

Add missing include and fixing CI problem observed with AliceO2Group/AliceO2#15745

Author: sawenzel

Framework/test/testCcdbDatabase.cxx

@@ -35,6 +35,7 @@
 #include <TROOT.h>
 #include <CCDB/CcdbApi.h>
 #include <cstdlib>
+#include <thread>
 
 namespace utf = boost::unit_test;