Deprecate support for designate-zone-manager

... because the process was deprecated in Newton and was removed in
Train by [1].

[1] 52ad1c4c13d1fead646435634e4b07bb32c68d28

Closes-Bug: #1962645
Change-Id: I9f5cbe14b311563aa75be2cbde79b0b4fe33c1ea

manifests/zone_manager.pp

@@ -1,5 +1,5 @@
 # == Class designate::zone_manager
-#
+# DEPRECATED !!
 # Configure designate zone manager service
 #
 # == Parameters
@@ -47,6 +47,8 @@ class designate::zone_manager (
   $export_synchronous        = $::os_service_default,
 ) inherits designate::params {
 
+  warning('The designate::zone_manager class has been deprecated.')
+
   designate_config {
     'service:zone_manager/workers'            : value => $workers;
     'service:zone_manager/threads'            : value => $threads;

releasenotes/notes/deprecate-zone_manager-b219dc5dde23e42f.yaml

@@ -0,0 +1,4 @@
+---
+deprecations:
+  - |
+    The ``designate::zone_manager`` class has been deprecated.