Remove getSfInstance usage from ViewRootImpl

The getSfInstance usage on ViewRootImpl is target to reduce jank
when moving split divider, but legacy split is going to be depracated
and it didn't used on new split too so we can remove whole related
codes safely.

Bug: 222696368
Test: build pass
Change-Id: Icf9b543bdd1d4bee54efb3be852722f247d1bd47