Update submodules: plugins (new commits)

plugins:
    894fb42 Chris Smith <chris@dmdirc.com>
            Tidy up topic handling.

            Depends-On: I9e8723fe0fe2b9209a401d33361f80fb832b9434
            Gerrit: http://gerrit.dmdirc.com/3414

    aede63c Greg Holmes <greg@dmdirc.com>
            Remove PreferencesManager singleton.

            Gerrit: http://gerrit.dmdirc.com/3413

Change-Id: I679159f03dafa4636bb658b8d239300e860fea53

modules/plugins

@@ -1 +1 @@
-Subproject commit 11ac6fc7e574993dd2eadef8dcce0b1098fd2497
+Subproject commit 894fb4279c6e151dfe479f6c4ce54b55322ba173