Revert "docs: Add an upgrade doc note about Glance show_multiple_locations"

This reverts commit 99838a8.

It applies to the Zed upgrade, not Antelope.

Author: markgoddard

doc/source/operations/upgrading.rst

@@ -162,20 +162,6 @@ environment. This can result in significant changes to the Kolla config. Take
 extra care when creating the Antelope branch of the kayobe-config and always
 check the config diff.
 
-Glance show_multiple_locations disabled
----------------------------------------
-
-Kolla Ansible no longer sets ``show_multiple_locations = True`` in Glance by
-default when Glance's Ceph RBD backend is enabled. This was applied as a fix
-but operators must note that this, in turn, disables Cinder and Nova's
-optimisations. In particular, this can increase instance creation times due to
-a lack of copy-on-write.
-
-On the other hand, these optimisations might have been causing other trouble
-for operators. Please see `LP#1992153
-<https://bugs.launchpad.net/kolla-ansible/+bug/1992153>`__. Operators relying
-on this feature can set the flag themselves using service config overrides.
-
 Known issues
 ============