Add metadata for Monitor::Health ownership

Claiming this page for the Monitor stage and the Health team.

doc/api/error_tracking.md

+---
+stage: Monitor
+group: Health
+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/#designated-technical-writers
+---
+
 # Error Tracking settings API
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/34940) in GitLab 12.7.