Is this on the JFBConnect registration page, or a different page? Also, do you know what extension is adding that field to the registration? Are you integrating with Community Builder, JomSocial, etc? Likely, you'll just need to remove the language string in that other extension that is inserting that text on the page. Without knowing what you're integrating with, I can't really give any specific advice right now though.
Thanks,
Alex