Clang: Remove old CPP code

It was there to suppress warnings but this is now done with compiler
arguments.

Change-Id: I62edae9c115c09aa07601547159c04e038943a9b
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>

src/tools/clangrefactoringbackend/source/locationsourcefilecallbacks.cpp

@@ -27,23 +27,9 @@
 
 #include "macropreprocessorcallbacks.h"
 
-#if defined(__GNUC__)
-#    pragma GCC diagnostic push
-#    pragma GCC diagnostic ignored "-Wunused-parameter"
-#elif defined(_MSC_VER)
-#    pragma warning(push)
-#    pragma warning( disable : 4100 )
-#endif
-
 #include <clang/Frontend/CompilerInstance.h>
 #include <clang/Lex/Preprocessor.h>
 
-#if defined(__GNUC__)
-#    pragma GCC diagnostic pop
-#elif defined(_MSC_VER)
-#    pragma warning(pop)
-#endif
-
 #include <memory>
 
 namespace ClangBackEnd {