Update submodules: plugins (new commits)

plugins:
    5669e78 Chris Smith <chris@dmdirc.com>
            Fix up DebugTest.

            Fix ambiguous verify calls that somehow work on J7 but not J8.

            Tidy imports, use Guava Sets instead of icky AICs.

            Gerrit: http://gerrit.dmdirc.com/3564

Change-Id: Ibc04f6e5bbec39fc0524307f68a4c8d569fe006d