[PR] Remove unnecessary folder from Makefile
[PR] Remove unnecessary folder from Makefile

Summary:
D14339975 just added the new folder, but didn't remove the now-unnecessary one.

Pull Request resolved: https://github.com/facebook/flow/pull/7531

Reviewed By: CatherineGasnier

Differential Revision: D14354388

Pulled By: nmote

fbshipit-source-id: 6432f29d67871423f57e10400de146fee36cda86

nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow