Revert "[FlexibleHeader] Fix bug where shadow layer's opacity wouldn'…

…t be set without a tracking scroll view. (#3201)" (#3225)

This change is resulting in "stacked" shadows when an MDCAppBar is above an
MDCTabBar.  In the particular case of Tabs below an MDCAppBar, the shadow effect is discouraged in designs. We may need to provide client teams with advice on how to integrate MDCAppBar and MDCTabBar in a way that still permits the App Bar to cast a shadow on other (non-scrollable) views in an appropriate way.

This reverts commit d0af3a7.

Reverts #3201

components/FlexibleHeader/src/MDCFlexibleHeaderView.m

@@ -911,7 +911,6 @@ - (void)fhv_accumulatorDidChange {
 
 - (void)fhv_updateLayout {
   if (!_trackingScrollView) {
-    [self fhv_commitAccumulatorToFrame];
     return;
   }