[documentation] Update fields.yml with official titles

[VihasMakwana]

I'm not sure where we'd have to make the change, but it would be great if we could make sure these product names use the official format. However, that shouldn't block this PR.

Originally posted by @colleenmcginnis in https://github.com/elastic/beats/pull/44858#discussion_r2152495171

[elasticmachine]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)

[damingupup]

HI bro! How do you add label? I don't seem to have permission to add them

[pierrehilbert]

What kind of label would you like to add?