[clutter] docs: Fix typo in Environment Variables (gsk->gdk)

[Andre Klapper <aklapper src gnome org>]

commit afc3ca9b2b1c6c1671b4a79777267d9d9a7e1621
Author: Justin Kim <justin kim collabora com>
Date:   Mon Jul 18 16:39:50 2016 +0900

    docs: Fix typo in Environment Variables (gsk->gdk)

 doc/reference/running-clutter.xml |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/doc/reference/running-clutter.xml b/doc/reference/running-clutter.xml
index 2d782b3..ca50218 100644
--- a/doc/reference/running-clutter.xml
+++ b/doc/reference/running-clutter.xml
@@ -38,7 +38,7 @@
               <listitem><simpara>wayland, for the Wayland backend</simpara></listitem>
               <listitem><simpara>win32, for the Windows backend</simpara></listitem>
               <listitem><simpara>osx, for the MacOS X backend</simpara></listitem>
-              <listitem><simpara>gsk, for the GDK backend</simpara></listitem>
+              <listitem><simpara>gdk, for the GDK backend</simpara></listitem>
               <listitem><simpara>eglnative, for the EGL/KMS backend</simpara></listitem>
               <listitem><simpara>cex100, for the CEx100 backend</simpara></listitem>
             </itemizedlist>