Fix start call resizing improperly with wrapping text.

app/src/main/res/layout/webrtc_call_view.xml

@@ -289,6 +289,7 @@
             android:paddingEnd="16dp"
             android:paddingBottom="32dp"
             android:visibility="gone"
+            android:gravity="center"
             app:layout_constraintBottom_toBottomOf="parent"
             app:layout_constraintEnd_toEndOf="parent"
             app:layout_constraintStart_toStartOf="parent"