GraphQL: Remove experiment status for some runner types

What does this MR do and why?

This MR removes the experiment status for some runner-related types which have been in production for a long time, and for which there is little chance that we'll be removing/performing changes to.

Changelog: added

Screenshots or screen recordings

Field	Usage
CiRunner.creationMethod (link) - not removing this since we only have 1 user (who requested this), and I'm not sure if it'll be useful once we remove support for registration tokens
CiRunner.creationStatus (link)

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