Remove internal_setarch option?

[scop]

At least the documentation of internal_setarch is outdated in etc/mock/site-defaults.cfg: it always defaults to True, and ctypes is a hard dependency anyway.

But before I go fix the doc: is the whole option outdated? py/mock.py sets personality if it's True, but is there a downside in just always doing that?

[xsuchy]

Yes. I think it can be safely removed.