Modified the last-call announcement template, at the IESG's request, removing the link to documment's ballot (which may not exist at the time last-call goes out). Fixes ietf-tools#2967. Commit ready for merge.

 - Legacy-Id: 17709

Author: rjsparks

ietf/templates/doc/mail/last_call_announcement.txt

@@ -22,8 +22,6 @@ Abstract{{ docs|pluralize }}
 The file{{ urls|pluralize }} can be obtained via
 {% for u in urls %}{{ u }}
 {% endfor %}
-IESG discussion can be tracked via
-{{ doc_url }}
 
 {% if ipr_links %}The following IPR Declarations may be related to this I-D: