Remove redundant return value in $.Callbacks

[dcherman]

 https://github.com/jquery/jquery/blob/master/src/callbacks.js#L213-215

fireWith already returns this, so you can save a couple of bytes by changing fire to just return self.fireWith( this, arguments );

[dcherman]

Ugh never mind, close this as invalid please.

Should have tested this locally first, it breaks the Deferred chainability tests.

[dmethvin]

And that's why we test. :)