[EZ] Remove `experimental.new_check` config
[EZ] Remove `experimental.new_check` config

Summary:
Changelog: [internal]

Found this when I'm trying to flip the default of inference_mode. This config should already been dead for quite a long time.

Reviewed By: panagosg7

Differential Revision: D38461965

fbshipit-source-id: 4ce22b4f80f74d3f4ef18f8889733a223f596ac4

facebook/flow,facebook/flow,mroch/flow,facebook/flow,facebook/flow,mroch/flow,mroch/flow,facebook/flow,mroch/flow,mroch/flow,facebook/flow,facebook/flow,mroch/flow,mroch/flow