Correct link to placement upgrade notes
Correct link to placement upgrade notes

In the depends-on the upgrade notes in placement are moved to a
different URL. Because the link here in nova was to an anchor, not
a URL, a redirect on the placement side will not catch this, so
explicitly update the link.

Depends-On: https://review.opendev.org/683783
Change-Id: Ib07eacb9150bbb8b0726cfe06ae334c7a764955c

klmitch/nova,mahak/nova,rahulunair/nova,rahulunair/nova,openstack/nova,openstack/nova,mahak/nova,klmitch/nova,openstack/nova,klmitch/nova,rahulunair/nova,klmitch/nova,mahak/nova