Update submodules: plugins (new commits)

plugins:
    0e4e578 Chris Smith <chris@dmdirc.com>
            Remove all IdentityManager references from plugins

            Everything now references an IdentityController or IdentityFactory,
            and obtains them by injection (or local plugin state) rather than
            using a singleton method.

            Gerrit: http://gerrit.dmdirc.com/2751

Change-Id: I31ba535033101c67d0e6d3dc3d8a0b30252eddc2