Update monitoring HTTP end point

This commit changes /_xpack/monitoring/_bulk to /_monitoring/bulk.
The former is deprecrated as 7.0.0.

Relates elastic/elasticsearch#36130
Relates elastic/elasticsearch#35958

Fixes #10528

Author: jakelandis

x-pack/lib/template.cfg.erb

@@ -13,7 +13,7 @@ input {
 output {
   elasticsearch {
     hosts => <%= es_hosts %>
-    bulk_path => "/_xpack/monitoring/_bulk?system_id=logstash&system_api_version=<%= system_api_version %>&interval=1s"
+    bulk_path => "/_monitoring/bulk?system_id=logstash&system_api_version=<%= system_api_version %>&interval=1s"
     manage_template => false
     document_type => "%{[@metadata][document_type]}"
     index => ""