Draft: Update working_with_agent.md

What does this MR do and why?

Describe in detail what your merge request does and why.

Changes the value in a example, according to the codebase

From:

#Invalid
grpc_level: warning

To:

#Valid
grpc_level: warn

The former results in a error:

"error":"failed to parse agent configuration: protojson.Unmarshal: proto: (line 1:84): invalid value for enum type: \"warning\"

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.