[DocsUI] Fix NavigationViewManagerTest failure on R

The "appBarLayout.setExpanded" logic added in CL:34832836 relies on
"mCurrentVerticalOffset" value to trigger, previously the value change
was put behind the "isAtLeastS()" check which causes this logic not
to run on Android R, which causes the corresponding unit test fail on
Android R. This CL moves the logic out of the "isAtLeastS()" check.

Bug: 436877182
Test: atest DocumentsUIGoogleTests:com.android.documentsui.NavigationViewManagerTest#testCollapsedAppBar_expandsOnFocus
Flag: com.android.documentsui.flags.use_material3
Change-Id: Ie2c0dd7f086a7ed0943623b1e4ad383d71b84a8e