Update submodules: plugins (new commits)

plugins:
    9c6e066 Greg Holmes <greg@dmdirc.com>
            Move licenses for  freedesktop notifications plugin.

            Gerrit: http://gerrit.dmdirc.com/4051

Change-Id: I4cc492ec26ecf64322f3dcf5e5bcb57d6609e93c

modules/plugins

@@ -1 +1 @@
-Subproject commit d3f6d41c3fab666d98b3fcf51cd8d4a18107a750
+Subproject commit 9c6e06630e2aa63903a6bb3f655435783ba2046f