confirmation: Remove vestiges of the MitUser table.

The MitUser table was removed in df525ad.

confirm_mituser.html could have been accessed through the last few lines of
confirmation/views.py:
    templates.insert(0, 'confirmation/confirm_%s.html'
                     % (obj._meta.model_name,))

The commit message on df525ad suggests there was another way
confirm_mituser.html could have been called, but I don't currently see
evidence for it in the code.

templates/confirmation/confirm_mituser.html

@@ -1,14 +0,0 @@
-{% extends "zerver/base.html" %}
-
-{% block content %}
-
-<form id="register" action="/accounts/register/" method="post">
-    {{ csrf_input }}
-    <input type="hidden" value="{{ key }}" name="key"/>
-    <input type="hidden" value="1" name="from_confirmation"/>
-</form>
-
-<script type="text/javascript">
-    $("#register").submit();
-</script>
-{% endblock %}

zerver/management/commands/export.py

@@ -31,7 +31,7 @@ class Command(BaseCommand):
       metadata needed to restore them even in the ab
 
     Things that are not exported:
-    * Confirmation, MitUser, and PreregistrationUser (transient tables)
+    * Confirmation and PreregistrationUser (transient tables)
     * Sessions (everyone will need to login again post-export)
     * Users' passwords and API keys (users will need to use SSO or reset password)
     * Mobile tokens for APNS/GCM (users will need to reconnect their mobile devices)

zerver/tests/test_templates.py

@@ -58,7 +58,6 @@ class TemplateTestCase(ZulipTestCase):
 
         logged_out = [
             'confirmation/confirm.html',  # seems unused
-            'confirmation/confirm_mituser.html',  # seems unused
             'zerver/compare.html',
             'zerver/landing_nav_blue.html',
             'zerver/footer.html',