[gnome-builder] docs: update sample plugin to work with completion provider changes

[Christian Hergert <chergert src gnome org>]

commit 791adc8f82cb85be40325fa6af84b4e4b473e7cd
Author: Christian Hergert <chergert redhat com>
Date:   Sun Oct 18 10:08:52 2015 -0700

    docs: update sample plugin to work with completion provider changes
    
    When we required that Ide.CompletionProvider be used, we forgot to update
    the sample plugin. This should get the sample working again.

 .../plugins/sample-plugin/sample_plugin.py         |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/doc/examples/plugins/sample-plugin/sample_plugin.py 
b/doc/examples/plugins/sample-plugin/sample_plugin.py
index e19644d..7c6b5aa 100644
--- a/doc/examples/plugins/sample-plugin/sample_plugin.py
+++ b/doc/examples/plugins/sample-plugin/sample_plugin.py
@@ -62,7 +62,7 @@ class EditorViewAddin(GObject.Object, Builder.EditorViewAddin):
     def do_unload(self, editor):
         pass
 
-class CompletionProvider(Ide.Object, Ide.CompletionProvider):
+class CompletionProvider(Ide.Object, GtkSource.CompletionProvider, Ide.CompletionProvider):
     # See GtkSource.CompletionProvider for all the things you can do.
 
     # NOTE: You must set X-Completion-Provider-Languages in .plugin file!