[Adaptive][Side Sheet] Added explicit style definition to coplanar sheet catalog demo.

The coplanar sheet catalog demo was missing an explicit style definition, which was causing some attributes like the background to display improperly.

PiperOrigin-RevId: 494217653
(cherry picked from commit 2752958)

Author: afohrman

catalog/java/io/material/catalog/sidesheet/res/layout/cat_sidesheet_fragment.xml

@@ -104,6 +104,7 @@
 
   <LinearLayout
     android:id="@+id/coplanar_side_sheet_container"
+    style="@style/Widget.Material3.SideSheet"
     android:layout_width="256dp"
     android:layout_height="match_parent"
     android:layout_gravity="end"