Merge branch 'docs-do-metadata-add' into 'master'

Add metadata to Digital Ocean doc page

See merge request gitlab-org/gitlab!76367

doc/install/digitaloceandocker.md

 ---
-stage: none
-group: unassigned
+stage: Enablement
+group: Distribution
 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
-type: howto
 ---
 
 # Digital Ocean and Docker Machine test environment **(FREE SELF)**