Revert "Specialise removeConst for nullptr"

This reverts commit b6e7c9bd7a in order to
be able to revert the commit it modifies in the upcoming commit.

include/internal/catch_evaluate.hpp

@@ -39,9 +39,6 @@ namespace Internal {
 
     template<typename T>
     T& removeConst(T const &t) { return const_cast<T&>(t); }
-#ifdef CATCH_CONFIG_CPP11_NULLPTR
-    inline std::nullptr_t removeConst(std::nullptr_t) { return nullptr; }
-#endif
 
 
     // So the compare overloads can be operator agnostic we convey the operator as a template