Updating security reachout email

[varun-lodaya]

Description

Updating security reach out email address from aws-security@amazon.com to security@opensearch.org.

Issues Resolved

N/A

Check List

• ~[ ] New functionality includes testing.~
  • ~[ ] All tests pass~
• [x] New functionality has been documented.
  • ~[ ] New functionality has javadoc added~
• [x] Commits are signed per the DCO using --signoff

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