Mark page as belonging to Release Management

Per the PM, this page belongs to the Release Management group.

doc/ci/environments/deployment_safety.md

+---
+stage: Release
+group: Release Management
+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
+---
+
 # Deployment safety
 
 Deployment jobs can be more sensitive than other jobs in a pipeline,

doc/security/cicd_environment_variables.md

 ---
-type: reference
+stage: Release
+group: Release Management
+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
 ---
 
 # CI/CD Environment Variables