Remove wchar_t* buffer from scanf format fix-it test.

Amends r204300 to not try to test fixing a wchar_t* to "%ls", which we don't
do correctly anyway. In C mode, wchar_t is just a typedef for a normal
primitive integer type, not a distinct type like it is in C++. To make this
work correctly, we'll need to look for the wchar_t typedef, not just the
builtin type.

Should fix the buildbots.