Update submodules: plugins (new commits)

plugins:
    273acf6 Chris Smith <chris@dmdirc.com>
            Inject more things into the DCC manager.

            Also deprecate the getters in the SwingController that should be
            avoided in favour of injection.

            Gerrit: http://gerrit.dmdirc.com/3035

Change-Id: I42c2bd2be1be3932626f2b06fd0a4178cebd6070