Tried this but could not get to work https://github.com/NobahdiAtoll/MusicBrainzPicardPlugins
For your case you could use scripting, e.g.
This should capture a few variants, such as “feat.”, “ft.”, “Feat.” and “feat.”. If I understand it correctly you are trying to remove this from existing tags and don’t tag against MusicBrainz metadata. If this is the case you need to run the script manually for your files. Add the above to a new script in Options > Scripting, give it a nice name (e.g. “Remove Ft. from artist”). Then you can right click your files loaded into Picard and select Run script -> “Remove Ft. from artist”
See also my comment here: