Update submodules: plugins (new commits)

plugins:
    9538500 Chris Smith <chris@dmdirc.com>
            Allow the clover licence to be set explicitly.

            Gerrit: http://gerrit.dmdirc.com/2732

Change-Id: Id6e8c87f639eb988646ebfb659849c9466c0395d

modules/plugins

@@ -1 +1 @@
-Subproject commit 23276790c42b8bc36707b98f2f7a8a8ea0853e53
+Subproject commit 9538500467f520a0b18089e0382f80a15af1e0cc