Remove getMessageSvc uses in AthMessaging constructor

With !53186 (merged) it is no longer necessary to pass the MessageSvc pointer to AthMessaging. This MR changes

#include "AthenaKernel/getMessageSvc.h"

MyClass::MyClass() :
  AthMessaging(Athena::getMessageSvc(), "MyClass")

to

MyClass::MyClass() :
  AthMessaging("MyClass")

across the entire repository.