Remove odd spacing after the divider

Two strategies for this UI problem

- If "PreferenceCategory" is an anchor for loading dynamical preferences,
we keep this preference category and then assign a no spacing layout to
it.

- If the cases only want to have a divider, we remove this preference category.
And then use allowDividerBelow or allowDividerAbove attribute.

Test: visual
Fixes: 130246959

Change-Id: I227fef20f5255159e4ab9a5add43a04b94e9b19a