Merge branch 'docs-remove-gitlab-eventstore-subscriber' into 'master'

Document how to remove a subscriber in Gitlab::EventStore

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/172042



Merged-by: Fabio Pitino <fpitino@gitlab.com>
Approved-by: Dylan Griffith <dyl.griffith@gmail.com>
Approved-by: John Mason <9717668-johnmason@users.noreply.gitlab.com>