Revert Register Akismet Anti-Spam as a connector.

This reverts [62193]. The connector for Akismet shouldn't show up when akismet is not installed. The plugin itself can register the connecter when it is activated.

Follow-up to [62193].

See #65012.
Props peterwilsoncc, jorgefilipecosta, johnbillion, eclev91, desrosj, davidbaumwald, jorbin.



git-svn-id: https://develop.svn.wordpress.org/trunk@62210 602fd350-edb4-49c9-b593-d223f7449a82