Use composer override instead of generate a patch for PHP class

[zgq354]

Creating and editing a patch file may not be very maintainable, it would be better to save and edit a full `.php' file.

example: https://github.com/FriendsOfFlarum/nightmode/blob/fcc97af9028a9ff7dda00cf74392fae10432fc3d/composer.json#L63-L67

ref: https://discuss.flarum.org/d/30868-completely-disable-s9e-text-formatter/2