Revert "Add workaround for keystonemiddleware/neutron memcached issue"

The default configuration was changed to use the advanced cache pool in
keystonemiddleware 9.3.0 (Xena release) [1].

This reverts commit 5a52d8e4 (except the
release note).

[1] https://review.opendev.org/c/openstack/keystonemiddleware/+/773939

Change-Id: I290d0a81c57c189b6eb62fc3eee3ed19f441671b

ansible/roles/neutron/templates/neutron.conf.j2

@@ -122,9 +122,6 @@ memcache_secret_key = {{ memcache_secret_key }}
 
 memcached_servers = {% for host in groups['memcached'] %}{{ 'api' | kolla_address(host) | put_address_in_context('memcache') }}:{{ memcached_port }}{% if not loop.last %},{% endif %}{% endfor %}
 
-# Workaround for https://bugs.launchpad.net/keystonemiddleware/+bug/1883659
-memcache_use_advanced_pool = True
-
 [oslo_messaging_notifications]
 transport_url = {{ notify_transport_url }}
 {% if neutron_enabled_notification_topics %}