Remove "Enable widgets" checkbox from Face Unlock settings

It doesn't work anyway as we have a different option to control
widgets' behaviour.

Change-Id: I2f3c2b6f8f638c6c4d9d9c9b3cdb2facfef70039
Merge "Remove "Enable widgets" checkbox from Face Unlock settings" into cm-11.0
Merge branch 'cm-11.0' into martincz