Use the stable 0.6.1 stack resource in versioned docs

[sbaum1994]

Summary

The versioned 0.6.1 self-managed documentation still references the 0.6.1 release-candidate stack resource. After the 0.6.1 documentation route is promoted, the manifest and download examples must use the stable 0.6.1 resource.

Acceptance criteria

• Set the self-managed stack version and distribution path to 0.6.1 in the 0.6.1 artifact manifest.
• Set the stack download examples to 0.6.1.
• Remove remaining release-candidate references from the 0.6.1 documentation text.

Related pull requests

• Depends on docs(self-managed): promote 0.6.1 as latest stable #605.