Add rate limiting info to elasticsearch setup

What does this merge request do and why?

The groupglobal search team discussed adding these instructions to Elastisearch setup. Code reviewers have commented on hitting the rate limit while reviewing our team's MRs and we felt it could be helpful to add to documentation

How to set up and validate locally

N/A

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Merge request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise an issue to follow-up.
• Documentation added/updated, if needed.
• Announcement added, if change is notable.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.