Update submodules: plugins (new commits)

plugins:
    4e26f8a Greg Holmes <greg@dmdirc.com>
            Don't set title pointlessly.

            Fixes-Issue: CLIENT-527
            Gerrit: http://gerrit.dmdirc.com/3754

Change-Id: I8dad2c4c9f80ab5dcbf88418c7b22c60ad639e83