[gtk+] fix the docs build

[Matthias Clasen <matthiasc src gnome org>]

commit d400c50ca3bb38ddc077d2076bdb54d47c374df6
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Feb 5 20:24:40 2018 +0100

    fix the docs build
    
    The GtkPlacesSidebar does not exist anymore in public API.

 docs/reference/gtk/gtk4-docs.xml |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)
---
diff --git a/docs/reference/gtk/gtk4-docs.xml b/docs/reference/gtk/gtk4-docs.xml
index c953d86..77056be 100644
--- a/docs/reference/gtk/gtk4-docs.xml
+++ b/docs/reference/gtk/gtk4-docs.xml
@@ -208,7 +208,6 @@
       <xi:include href="xml/gtkfontbutton.xml" />
       <xi:include href="xml/gtkfontchooserwidget.xml" />
       <xi:include href="xml/gtkfontchooserdialog.xml" />
-      <xi:include href="xml/gtkplacessidebar.xml" />
     </chapter>
 
     <chapter id="Ornaments">