[gnome-builder] doc: remove unused section

[Christian Hergert <chergert src gnome org>]

commit 50fe8ef53a405256bf8754d24b24634df0365552
Author: Christian Hergert <chergert redhat com>
Date:   Wed Sep 6 14:58:15 2017 -0700

    doc: remove unused section
    
    This would be less useful since we have examples for perspectives and
    panels now.

 doc/plugins/workbench/index.rst   |    1 -
 doc/plugins/workbench/widgets.rst |   21 ---------------------
 2 files changed, 0 insertions(+), 22 deletions(-)
---
diff --git a/doc/plugins/workbench/index.rst b/doc/plugins/workbench/index.rst
index ab83098..3ea91db 100644
--- a/doc/plugins/workbench/index.rst
+++ b/doc/plugins/workbench/index.rst
@@ -9,7 +9,6 @@ Extending the Workbench
    basics
    actions
    headerbar
-   widgets
    perspectives
    panels