Remove static_hermes_staging variant for Fantom tests (#52861)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/52861

Changelog: [internal]

We added this mode recently to support all local Hermes variants, but this doubles the number of build type combinations which regresses test execution time and give us little benefit, so we're removing it.

Reviewed By: rshest

Differential Revision: D79080370

fbshipit-source-id: e1b536427acb98ec01edfd44829e2fef9be9b18d