Reverted a change from [5602], reinstating the explicit To: field for

last-call announcements, because removing it caused the copies of the
announcements destined for email lists to be held by Mailman for
moderation because of implicit destination.  Relates to issue ietf-tools#811.
 - Legacy-Id: 5684
Note: SVN reference [5602] has been migrated to Git commit 19dcf10

Author: levkowetz

ietf/templates/idrfc/last_call_announcement.txt

@@ -1,7 +1,6 @@
 {% load ietf_filters %}{% load mail_filters %}{% autoescape off %}From: The IESG <noreply@ietf.org>
-To: IETF-Announce:; {% if cc %}
+To: IETF-Announce <ietf-announce@ietf.org> {% if cc %}
 CC: {{ cc }}{% endif %}
-Bcc: <ietf-announce@ietf.org>
 Reply-To: IETF Discussion List <ietf@ietf.org>
 Sender: <iesg-secretary@ietf.org>
 Subject: Last Call: {{ doc.file_tag }} ({{ doc.title|clean_whitespace }}) to {{ doc|std_level_prompt }}