Merge branch 'doc-update-group-label-container' into 'master'

Doc: Update metadata group label

See merge request gitlab-org/gitlab!37140

doc/user/project/clusters/securing.md

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 stage: Defend
-group: container_security
+group: Container Security
 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
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