registration: restore paragraph/bold style in completion message (#50700)

src/authentic2/templates/registration/registration_complete.html

@@ -10,6 +10,7 @@
   <p>{% blocktrans %}<strong>Your registration request has been refused.</strong> Indeed your browser checked a hidden anti-robot checkbox on the registration form. A browser extension may produce this behaviour, in this case disable such extensions and try again.{% endblocktrans %}</p>
   {% else %}
   {% block instructions %}
+  <p><strong>
   {% blocktrans with email=request.session.registered_email %}
   An email was sent to {{ email }}.
   {% endblocktrans %}