documentation/poky-ref-manual/introduction.xml: [BUGID# 553] - Fixed pokylinux URL

[BUGID# 553] - In the Development Checkouts section (1.5.3)
    there is a reference to
    http://git.pokylinux.org/.  This URL resolves to an older looking
    source area.  I determined that the URL
    http://git.yoctoproject.org/ resolves to the newer Yocto source
    web interface so I changed the URL to that.
    This is a partial fix
    to Bug 553.

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>

documentation/poky-ref-manual/introduction.xml

@@ -153,7 +153,7 @@
         <para>
             Poky is available from our git repository located at
             git://git.pokylinux.org/poky.git; a web interface to the repository
-            can be accessed at <ulink url='http://git.pokylinux.org/'/>.
+            can be accessed at <ulink url='http://git.yoctoproject.org/'/>.
         </para>
 
         <para>