fix lint error

Author: ajungg

ui/src/main/res/layout/snabble_view_payment_credentials_list.xml

@@ -27,7 +27,7 @@
             android:layout_height="wrap_content"
             android:layout_margin="16dp"
             android:layout_gravity="center_horizontal"
-            android:tint="?attr/colorOnSurface"
+            app:tint="?attr/colorOnSurface"
             android:src="@drawable/snabble_ic_creditcard"/>
 
         <TextView