For #9359: Revert 8491.

In the UX review of 8491 it was discovered that the proposed solution is not
optimal and we should actually better stick with the old implementation.

This ticket comes to help with that and revert the already merged patch for
8491 and so will add same gradient to the top toolbar as the bottom toolbar.

app/src/main/res/drawable/private_home_bottom_bar_background_gradient_top.xml

@@ -6,7 +6,12 @@
 <layer-list xmlns:android="http://schemas.android.com/apk/res/android">
 <item>
     <shape>
-        <solid android:color="@color/toolbar_end_gradient_private_theme"/>
+        <gradient
+            android:angle="45"
+            android:startColor="#7529A7"
+            android:centerColor="#492E85"
+            android:endColor="#383372"
+            android:type="linear" />
     </shape>
 </item>
 <item android:top="-2dp" android:left="-2dp" android:right="-2dp">