Revert "Cmb: Workaround for gcc 4.7 bug"

This reverts commmit e2d60fdcc3 because we
require "g++ 4.8 or later" nowadays.

Change-Id: I1ce7b37bbf8c73ce4466a35b36fd66e680339fe9
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/tools/clangbackend/ipcsource/projectpartsdonotexistexception.h

@@ -40,12 +40,6 @@ public:
 
     const char *what() const Q_DECL_NOEXCEPT override;
 
-#if defined(__GNUC__) && !defined(__clang__)
-#  if !__GNUC_PREREQ(4,8)
-    ~ProjectPartDoNotExistException() noexcept {}
-#  endif
-#endif
-
 private:
     Utf8StringVector projectPartIds_;
     mutable Utf8String what_;