claim.html: move command to a dedicated line

This way the command is easier to select, copy and paste by the readers.

Related to #47.

dm/templates/dm/claim.html

@@ -14,7 +14,9 @@ fix this situation.</p>
 <p>Since you are logged in, I already know that your Single Sign-On username is
 <b>{{identity.subject}}</b>. The missing bit of information is who are you in the site,
 and I would like to find out using your GPG key. Please enter the fingerprint
-in this form (just the hexadecimal digits, as in <code>gpg --fingerprint $YOUR_KEYID | sed -nre 's/Key fingerprint =//p'</code>):</p>
+in this form (just the hexadecimal digits, as in:</p>
+
+<pre>gpg --fingerprint $YOUR_KEYID | sed -nre 's/Key fingerprint =//p'</pre>
 
 <form action="" method="POST">{% csrf_token %}
 {{form.as_p}}