Update submodules: plugins (new commits)

plugins:
    4c9a1ce Greg Holmes <greg@dmdirc.com>
            Remove @ListenerSupport

            Gerrit: http://gerrit.dmdirc.com/2796

Change-Id: I380f5ba21337483acbc53f83b2daeec980ce0d5d
Remove @ListenerSupport.

Change-Id: Id1ed05dd9f4cd7114828ef064cc8189dde2a4450
Reviewed-on: http://gerrit.dmdirc.com/2797
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Greg Holmes <greg@dmdirc.com>