Fix dashboard icon on dark mode again
Fix dashboard icon on dark mode again

There was a generic filter in the past, but it was removed with
https://github.com/nextcloud/server/commit/1d35a53991f356976d78b8053651737821502687

So now we apply the filter at our best knowledge

Signed-off-by: Joas Schilling <ab43a7c9cb5b2380afc4ddf8b3e2583169b39a02@schilljs.com>

nextcloud/spreed,nextcloud/spreed,nextcloud/spreed