Update DocImpact notifier with new dest addr.

The openstack documentation team has a new mailing list in part to
accomodate the DocImpact notifier. Update the destination address in
the notify_doc_impact script to send mail to
openstack-docs@lists.openstack.org.

Change-Id: I041194298a18e5f710c6e3bd7221dee2099733e8
diff --git a/notify_doc_impact.py b/notify_doc_impact.py
index d969eb0..1d312ae 100755
--- a/notify_doc_impact.py
+++ b/notify_doc_impact.py
@@ -33,7 +33,7 @@
 Log:
 %s
 """
-DEST_ADDRESS = 'openstack-doc-core@lists.launchpad.net'
+DEST_ADDRESS = 'openstack-docs@lists.openstack.org'
 
 def process_impact(git_log, args):
     """Notify doc team of doc impact"""