Update submodules: plugins (new commits)

plugins:
    ca61346 Greg Holmes <greg@dmdirc.com>
            Tidy up TreeTreeScroller.

            Gerrit: http://gerrit.dmdirc.com/3678

Change-Id: Ib226edbd46dc3eeb9466ea70b0522918f02ace04

modules/plugins

@@ -1 +1 @@
-Subproject commit 782192e5fd60fd58ce0c88576e5d211ddfbcc40d
+Subproject commit ca6134670bdf53933cf76f0689edf98eb66e1798