Settings: Remove leftover from old theme chooser

Change-Id: Iaf97e2b94c27839eb4f9827a77917fe21a311b4c
Revert "Allow changing theme to Holo.Light without crashing"

http://review.cyanogenmod.org/#/c/70745/ solves the issue
that this patch originally was created for.

This reverts commit 8cc23d58abc4874fe049a8dfa70910cf0b5dd9b2.

Change-Id: Ia350a03749202a2c0ae809400a3ebb554551d601

Conflicts:

	res/values/themes.xml