Remove the "enable widgets" preference properly

779a6aed removed this preference in
favor of a switch in the CM lock screen section, but failed to do so for
all lock screen types. Remove the broken preference from every possible
lock type to avoid confusing a lot of people (i.e. me) with a broken
toggle.

Change-Id: Ib1544cd5dcccb77a8f7a70b820035cf16cf43589