Added a Limitations bullet noting that the per-response metrics block isn't populated for agentic requests

[smasurekar]

Description

Added a Limitations bullet noting that the per-response metrics block isn't populated for agentic requests

Checklist

• I am familiar with the Contributing Guidelines.
• All commits are signed-off (git commit -s) and GPG signed (git commit -S).
• New or existing tests cover these changes.
• The documentation is up to date with these changes.
• If adjusting docker-compose.yaml environment variables have you ensured those are mimicked in the Helm values.yaml file.