Updates on docs to remove out-of-date contents

[blrchen]

Description

Updates on docs to remove out of date contents

• Remove the content for using Elastic search as online store
• Remove the guidence not use sql registry for Prod

How was this PR tested?

Does this PR introduce any user-facing changes?

• No. You can skip the rest of this section.
• Yes. Make sure to clarify your proposed changes.

[jainr]

@blrchen - Could you please comment on why we removed the cosmosDBsink section from the docs?

[blrchen]

@blrchen - Could you please comment on why we removed the cosmosDBsink section from the docs?

Hello @jainr , thanks for raising this up. The CosmosDb section doc removal is by mistaken. I only intented to remove the Elastic Search section. Could you please help adding this back in your PRs?