Drop reference to removed admin page

[sentry-io[bot]]

The Section admin page was removed, but as before there were some hardcoded references to it in a template override. The reference should be removed.

It's here:

web/main/templates/admin/main/casebook/change_form.html
8:      <a href="{% url 'admin:main_section_changelist' %}?casebook={{ original.id }}&o=5">

Sentry Issue: H2O-AC

NoReverseMatch: Reverse for 'main_section_changelist' not found. 'main_section_changelist' is not a valid view function or pattern name.
(29 additional frame(s) were not displayed)
...
  File "django/template/base.py", line 938, in render
    bit = node.render_annotated(context)
  File "django/template/base.py", line 905, in render_annotated
    return self.render(context)
  File "django/template/defaulttags.py", line 449, in render
    url = reverse(view_name, args=args, kwargs=kwargs, current_app=current_app)
  File "django/urls/base.py", line 86, in reverse
    return resolver._reverse_with_prefix(view, prefix, *args, **kwargs)
  File "django/urls/resolvers.py", line 698, in _reverse_with_prefix
    raise NoReverseMatch(msg)

[bensteinberg]

I think we're still seeing this error as of this morning.