[Star Tree] Removal of @ExperimentalApi annotations in star-tree related code files

[sandeshkr419]

Is your feature request related to a problem? Please describe

Follow-up on #18070

Describe the solution you'd like

Since the star-tree is not feature-flagged as experimental anymore, we need to remove up @ExperimentalApi annotations across code-files across indexing and search.

Related component

No response

Describe alternatives you've considered

No response

Additional context

Since this change does not involves considerable logical planning, I feel this is a low-effort good first issue as well, which involves minor code change, running spotless, and raising a PR.

[happysubin]

Could you please assign this to me? I'd love to work on it !!

[sandeshkr419]

Thanks @happysubin for helping on this.

Feel free to ask any questions. @bharath-techie & I can help answer them and review the changes.

[aryaman-vohra]

Can you assign this task to me ? I would love to work on it .