set ic_warning color to colorError

it was purple in dark mode

tested by showing the delete note dialog in the reviewer

AnkiDroid/src/main/res/drawable/ic_warning.xml

@@ -3,7 +3,7 @@
         android:height="24dp"
         android:viewportWidth="24.0"
         android:viewportHeight="24.0"
-        android:tint="?attr/colorOnSurface">
+        android:tint="?attr/colorError">
     <path
         android:fillColor="@color/white"
         android:pathData="M1,21h22L12,2 1,21zM13,18h-2v-2h2v2zM13,14h-2v-4h2v4z"/>