ref-manual: Converted two external links to internal links.

(From yocto-docs rev: db050c85848f2e465b694f5caeefde478d984c1e)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/ref-manual/ref-classes.xml

@@ -16,7 +16,7 @@
 </para>
 
 <para>
-    Any <ulink url='&YOCTO_DOCS_REF_URL;#metadata'>Metadata</ulink> usually
+    Any <link linkend='metadata'>Metadata</link> usually
     found in a recipe can also be placed in a class file.
     Class files are identified by the extension <filename>.bbclass</filename>
     and are usually placed in a <filename>classes/</filename> directory beneath
@@ -2399,7 +2399,7 @@ This check was removed for YP 2.3 release
         all dependencies previously built.
         The reason for this discrepancy is because the RPM package manager
         creates and processes more
-        <ulink url='&YOCTO_DOCS_REF_URL;#metadata'>Metadata</ulink> than the
+        <link linkend='metadata'>Metadata</link> than the
         IPK package manager.
         Consequently, you might consider setting
         <filename>PACKAGE_CLASSES</filename> to "package_ipk" if you are