docs(argocd-apps): Add deprecated note for Argo CD Extensions

[yu-croco]

Related to https://github.com/argoproj/argo-helm/pull/2442#issuecomment-1905682988 .

Checklist:

• [x] I have bumped the chart version according to versioning
• [x] I have updated the documentation according to documentation
• [x] I have updated the chart changelog with all the changes that come with this pull request according to changelog.
• [x] Any new values are backwards compatible and/or have sensible default.
• [x] I have signed off all my commits as required by DCO.
• [x] My build is green (troubleshooting builds).