Draft: feat: remove line from Duo Chat that says MRs are not supported

What does this merge request do and why?

This removes the line from Duo Chat that says MRs are not supported.

Note: this should be merged after this MR has been **fully rolled out **

How to set up and validate locally

1. Enable 'v2_chat_agent_integration' FF on monolith
2. Go to a MR
3. Ask Duo Chat to summarize it
4. It should work

Merge request checklist

- [ ] Tests added for new functionality. If not, please raise an issue to follow up. - [ ] Documentation added/updated, if needed.