format.html.in: Kill useless spaces in <pre/>

The <pre/> section is rendered as-is on the page. That is, if all
the lines are prefixed with 4 spaces the rendered page will also
have them. Problem is if we put a box around such <pre/> because
the content might not fix into it.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

docs/format.html.in

@@ -38,7 +38,7 @@
     </p>
 
     <pre>
-      $ virt-xml-validate /path/to/XML/file</pre>
+$ virt-xml-validate /path/to/XML/file</pre>
 
   </body>
 </html>