Add new class wizard remembers removed classes as base classes

Reproduce:

1. Create Console Project from Wizard (qmake)
2. Add new class ClassB
3. Add new class ClassD derived from ClassB
4. Remove classd.cpp from project panel with "Remove" permanently
5. Accept to remove classd.h, too
6. Add new class ClassD2 derived from ... type Cla

ClassD will be offered.

This does not exist anymore.

Looks like there is some cache was not cleared when classd.cpp/h was removed permanently.