docs: hacking: remove note about rename detection

It has been enabled by default for over three years now:

commit 5d2a30d7d8777319c745804f040fa405d02169ce
Author:     Junio C Hamano <gitster@pobox.com>
CommitDate: 2016-04-03 10:29:22 -0700

    Merge branch 'mm/diff-renames-default'

https://github.com/git/git/commit/5d2a30d7d8777319c745804f040fa405d02169ceSigned-off-by: NJán Tomko <jtomko@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>
Reviewed-by: NAndrea Bolognani <abologna@redhat.com>

docs/hacking.html.in

@@ -29,11 +29,7 @@
         file from zanata.</p>
       </li>
 
-      <li><p>Post patches using <code>git send-email</code>, with git
-        rename detection enabled.  You need a one-time setup of:</p>
-<pre>
-  git config diff.renames true
-</pre>
+      <li><p>Post patches using <code>git send-email</code>.</p>
         <p>Also, for code motion patches, you may find that <code>git
         diff --patience</code> provides an easier-to-read patch.
         However, the usual workflow of libvirt developer is:</p>