[gtk+] Fix the docs build

[Matthias Clasen <matthiasc src gnome org>]

commit 3902a0d3b1f5b99d626052bf7b0e5be36a639aaa
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Dec 22 22:59:00 2017 -0500

    Fix the docs build
    
    We no longer have GtkClipboard.

 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 557207d..4bb2f0e 100644
--- a/docs/reference/gtk/gtk4-docs.xml
+++ b/docs/reference/gtk/gtk4-docs.xml
@@ -316,7 +316,6 @@
     <xi:include href="xml/gtkfeatures.xml" />
     <xi:include href="xml/gtkaccelgroup.xml" />
     <xi:include href="xml/gtkaccelmap.xml" />
-    <xi:include href="xml/gtkclipboard.xml" />
     <xi:include href="xml/gtkdnd.xml" />
     <xi:include href="xml/gtksettings.xml" />
     <xi:include href="xml/gtkbindings.xml" />