Genres are created in the database as a record when the first track containing that genre is added.
After that, the name of the genre is never updated, because it is shared by many tracks/albums/artists. So changing the spelling will probably have no effect unless you practically Plex Dance all tracks, albums, and artists which have the genre assigned to them.
The Plex Dance might even require you to wait up to a week before you can re-add the items, because the genre table is only purged once a week during automatic server maintenance.
