drowl_media: ^4 compatibility

Nice, we just verified that none of the three affected fields is directly used in here! :)

• field_document => field_media_document
• field_image => field_media_image
• field_video_file => field_media_video_file

So there doesn't seem to be any incompatibility 🎉

I'll add the compatibility in the info file here!

Automatically closed - issue fixed for 2 weeks with no activity.