The button title for removing oneself as a co-creator on the Edit Work page or the Edit Series page is titled "Remove Me As Author" and should be "Remove Me As Co-Creator."
Also, the success and error messages you get when using these buttons should refer to creators, not authors:
Successfully removing yourself from a series should be: You have been removed as a creator from the series and its works.
Unsuccessfully removing yourself from a series (because one of the works in said series has only you as a creator) should be: Sorry, we can't remove all creators of a work.
Successfully removing yourself from a work should be: You have been removed as a creator from the work.
The “Remove Me as Co-Creator” option on the mass edit page should have the “As” capitalized now. (You’ll need to select at least one work with a co-creator to make that option appear.)