ref-manual: Removed bugzilla.bbclass

The migration section noted this class as becoming obsolete.
I removed it from the class reference section.

(From yocto-docs rev: 2f1040b1e079eb9f661cc643326bd03514747e07)

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

documentation/ref-manual/ref-classes.xml

@@ -335,18 +335,6 @@
     </para>
 </section>
 
-<section id='ref-classes-bugzilla'>
-    <title><filename>bugzilla.bbclass</filename></title>
-
-    <para>
-        The <filename>bugzilla</filename> class supports setting up an
-        instance of Bugzilla in which you can automatically files bug reports
-        in response to build failures.
-        For this class to work, you need to enable the XML-RPC interface in
-        the instance of Bugzilla.
-    </para>
-</section>
-
 <section id='ref-classes-buildhistory'>
     <title><filename>buildhistory.bbclass</filename></title>