refactor: update helm chart version schema

[aabouzaid]

What's in this PR?

After the 8.4 release (January 2024), the Camunda Helm chart version is decoupled from the version of the application (e.g., the chart version is 9.0.0 and the application version is 8.4.x).

Checklist

Please make sure to follow our Contributing Guide.

Before opening the PR:

• In the repo's root dir, run make go.update-golden-only.
• There is no other open pull request for the same update/change.
• Tests for charts are added (if needed).
• In-repo documentation are updated (if needed).

After opening the PR:

• Did you sign our CLA (Contributor License Agreement)? It will show once you open the PR.
• Did all checks/tests pass in the PR?