Update submodules: plugins (new commits)

plugins:
    fdde3a5 Chris Smith <chris@dmdirc.com>
            Remove some usages of Main.

            Depends-On: I5f88cccf81f0fb80e2fcf915d453660d5690c8c0
            Gerrit: http://gerrit.dmdirc.com/2709

Change-Id: I51091051679fa8a9c1504f44326455b6fbbb9d64
Update submodules: plugins (new commits)

plugins:
    16b8ca9 Chris Smith <chris@dmdirc.com>
            Remove the Dummy UI.

            This was originally intended for testing purposes, but we can do that
            effectively with mocks. It's a pain to maintain and doesn't offer
            any real benefit.

            Gerrit: http://gerrit.dmdirc.com/2711

Change-Id: I90602ddf6ef3f7a9111163e90a7665fea1492f72