circle progress text not relevant for a18y (#418)

Corona-Warn-App/src/main/res/layout/view_circle_progress.xml

@@ -11,6 +11,7 @@
             style="@style/body2Medium"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
+            android:importantForAccessibility="no"
             app:layout_constraintBottom_toBottomOf="parent"
             app:layout_constraintEnd_toEndOf="parent"
             app:layout_constraintStart_toStartOf="parent"