Deprecate retire.js analyzer

Problem to solve

retire.js analyzer will be removed in 15.0 and this deprecation has to be announced.

Same process as for bundler-audit deprecation: #289832 (closed)

Proposal

Warn users about this deprecation in the analyzer itself and the DS documentation.

Implementation plan

• update Dependency Scanning docs with a warning about deprecation (see similar MR for bundler-audit: !76408 (merged))
  • also update the documentation about Javascript projects: https://docs.gitlab.com/ee/user/application_security/dependency_scanning/#javascript
• update the retire.js analyzer with a warning in the job output (see similar MR for bundler-audit: gitlab-org/security-products/analyzers/bundler-audit!88 (merged))
• add a deprecation items in Gitlab docs following https://about.gitlab.com/handbook/marketing/blog/release-posts/#deprecations and if users customized yml to update it and coverage is continued through gemnasium (see similar MR for bundler-audit: !76191 (merged))
• communicate to support slack channels and link to issue

Testing

• Confirm Dependency Scanning docs have a warning about retire.js deprecation: https://docs.gitlab.com/ee/user/application_security/dependency_scanning/#javascript
• Confirm the retire.js analyzer displays a deprecation warning in the job output
  • See example job: https://gitlab.com/gitlab-org/security-products/tests/js-npm/-/jobs/2084102387
• Confirm retire.js is added to Deprecated items: https://docs.gitlab.com/ee/update/deprecations#retire-js-dependency-scanning-tool
• Confirm #support has been informed that retire.js has been deprecated, with a link to this issue: https://gitlab.slack.com/archives/C01AQRPQ58C/p1645029909339809