Create Gitlab::RequestProfile page placeholder

The Gitlab::RequestProfile page was completely deleted
in https://gitlab.com/gitlab-org/gitlab/-/merge_requests/85890
but we now have a standardized process for docs of removed features:
https://docs.gitlab.com/ee/development/documentation/versions.html#remove-a-page

doc/administration/monitoring/performance/request_profiling.md

+---
+stage: Monitor
+group: Respond
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
+remove_date: '2022-07-26'
+redirect_to: 'index.md'
+---
+
+# Request profiling (removed) **(FREE SELF)**
+
+This feature was [deprecated](https://gitlab.com/gitlab-org/gitlab/-/issues/352488) in GitLab 14.8
+and [removed](https://gitlab.com/gitlab-org/gitlab/-/issues/350152) in 15.0.