Add documentation for IndexRepair task

What does this MR do and why?

Add documentation for IndexRepair task

This MR adds documentation for IndexRepair task.

References

• Add repair index tool (!196677 - merged)

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #6974 (closed)