Fix HUN input alignment with IME

SSA#updateHeadsUpStates defines the top HUN as having
    mustStayOnScreen = TRUE
    headsUpIsVisible = FALSE

However, SSA#updateChild sets
    headsUpIsVisible = TRUE
for the top HUN when shade is closed

When we tap the reply button and show IME, SSA#updateHeadsUpStates
does not recognize the top HUN as such and skips it when
reducing yTranslation by scrollY (which includes IME inset)

This change skips setting headsUpIsVisible on HUNs when shade is closed.

Fixes: 187485733
Test: expand HUN in portrait/landscape with largest font/display
      tap reply button to show IME
      => HUN shifts up to align bottom of input with top of IME
Change-Id: I236b01a7f9070ebe58457eab9ea8072703acb12c