Remove shuffle button since it doesn't work yet

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=164141326

library/ui/src/main/res/layout/exo_playback_control_view.xml

@@ -34,9 +34,6 @@
     <ImageButton android:id="@id/exo_rew"
       style="@style/ExoMediaButton.Rewind"/>
 
-    <ImageButton android:id="@id/exo_shuffle"
-      style="@style/ExoMediaButton.Shuffle"/>
-
     <ImageButton android:id="@id/exo_repeat_toggle"
       style="@style/ExoMediaButton"/>