Update submodules: plugins (new commits)

plugins:
    2ded792 Greg Holmes <greg@dmdirc.com>
            Tidy up alias manager dialog.

            Depends-On: Ic9c0091441d4f7d87ddc96a327f5e5b12b4cf803
            Gerrit: http://gerrit.dmdirc.com/3572

Change-Id: If86477180d00bca3f1bbd591cbfb1f1b06329c0c