Update index.md

[lack-of-gravity-jack]

Changes

update async consumes 2 requests units from the memory store quota for read and write

https://devforum.roblox.com/t/code-6-error-the-rate-of-requests-exceeds-the-allowed-limit-memory-store/1918436/14

Checks

By submitting your pull request for review, you agree to the following:

• [x] This contribution was created in whole or in part by me, and I have the right to submit it under the terms of this repository's open source licenses.
• [x ] I understand and agree that this contribution and a record of it are public, maintained indefinitely, and may be redistributed under the terms of this repository's open source licenses.
• [x ] To the best of my knowledge, all proposed changes are accurate.