hide spinner by default (#3193)

Co-authored-by: harambasicluka <64483219+harambasicluka@users.noreply.github.com>

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

@@ -48,6 +48,7 @@
         android:layout_height="wrap_content"
         android:layout_marginTop="@dimen/spacing_normal"
         android:indeterminate="true"
+        android:visibility="invisible"
         app:indicatorColor="@android:color/white"
         app:indicatorSize="64dp"
         app:trackColor="@android:color/transparent"