Added a link to usage ping

Trying to help alleviate confusion with
service ping and usage ping

doc/development/service_ping/index.md

@@ -6,7 +6,8 @@ info: To determine the technical writer assigned to the Stage/Group associated w
 
 # Service Ping Guide **(FREE SELF)**
 
-> Introduced in GitLab Ultimate 11.2, more statistics.
+> - Introduced in GitLab Ultimate 11.2, more statistics.
+> - In GitLab 14.1, [renamed from Usage Ping to Service Ping](https://gitlab.com/groups/gitlab-org/-/epics/5990). In 14.0 and earlier, use the Usage Ping documentation for the Rails commands appropriate to your version.
 
 Service Ping is a GitLab process that collects and sends a weekly payload to GitLab.
 The payload provides important high-level data that helps our product, support,