remove unnecessary conversion of newline to br tag

relic from when I was using div, not pre

IPython/html/templates/error.html

@@ -1,31 +1,31 b''
 {% extends "page.html" %}
 
 {% block login_widget %}
 {% endblock %}
 
 {% block stylesheet %}
 {{super()}}
 <style type="text/css">
 /* disable initial hide */
 div#header, div#site {
     display: block;
 }
 </style>
 {% endblock %}
 {% block site %}
 
 <div class="error">
     {% block h1_error %}
     <h1>{{status_code}} : {{status_message}}</h1>
     {% endblock h1_error %}
     {% block error_detail %}
     {% if message %}
     <p>The error was:</p>
     <div class="traceback-wrapper">
-    <pre class="traceback">{{message | replace('\n', '<br/>')}}</pre>
+    <pre class="traceback">{{message}}</pre>
     </div>
     {% endif %}
     {% endblock %}
 </header>
 
 {% endblock %}