widgets: Remove redundant equality check in SelectWithInputWidget

widgets: Remove redundant equality check in SelectWithInputWidget

The check `if ( $config['disabled'] == true )` is the same as the
check `if ( $config['disabled'] )`. Was this intentional or was it
supposed to be a test for equality and type (===)? If not, then I
think this patch removes the irrelevancy.

Clearly, if the $config['disabled'] is set to false, the isset()
check will return true but the second check will fail even with
this patch as it does the same thing.

Change-Id: Ibbe5b4949590f8ac954f613236056dd2e6dd18ba