Remove note about Azure ARM plugin (#40219)

Relates to #22679

docs/plugins/discovery-azure-classic.asciidoc

@@ -4,9 +4,7 @@
 The Azure Classic Discovery plugin uses the Azure Classic API to identify the
 addresses of seed hosts.
 
-// TODO: Link to ARM plugin when ready
-// See issue https://github.com/elastic/elasticsearch/issues/19146
-deprecated[5.0.0, Use coming Azure ARM Discovery plugin instead]
+deprecated[5.0.0, This plugin will be removed in the future]
 
 :plugin_name: discovery-azure-classic
 include::install_remove.asciidoc[]

plugins/discovery-azure-classic/src/main/java/org/elasticsearch/plugin/discovery/azure/classic/AzureDiscoveryPlugin.java

@@ -48,7 +48,7 @@ public class AzureDiscoveryPlugin extends Plugin implements DiscoveryPlugin {
 
     public AzureDiscoveryPlugin(Settings settings) {
         this.settings = settings;
-        deprecationLogger.deprecated("azure classic discovery plugin is deprecated. Use azure arm discovery plugin instead");
+        deprecationLogger.deprecated("azure classic discovery plugin is deprecated.");
         logger.trace("starting azure classic discovery plugin...");
     }