Update submodules: plugins (new commits)

plugins:
    7e157a8 Chris Smith <chris@dmdirc.com>
            Remove unused ConfigStats subcommand.

            Gerrit: http://gerrit.dmdirc.com/3082

Change-Id: Id46f63f9412a2de2bcfe123d58e8391d6946ec3b
Make ConfigManager package private.

Change-Id: I751cbc2354ddb3ea9a431d5b85eed72d9764fed9
Reviewed-on: http://gerrit.dmdirc.com/3081
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Greg Holmes <greg@dmdirc.com>