Please deactivate the following plugin(s) to make Ultimate Branding to work: Site Generator Replacem

In my settings I see this message:

Please deactivate the following plugin(s) to make Ultimate Branding to work:
Site Generator Replacement

Do you know why it's showing?

I disabled it and its still showing and when I see my HTML source code I still see the generator meta tag.

What does this tag do anyway?