Remove workaround for GC accounting bug
Remove workaround for GC accounting bug

Summary:
See D26341446 (https://github.com/facebook/flow/commit/6d81cd8bf4a0d439c461c5fc771ba4e2b027a2ee). We no longer need this workaround because the bug is fixed in
OCaml 4.12.1

Reviewed By: mroch

Differential Revision: D34278970

fbshipit-source-id: 211bd493c7806a15e2d31ae850b1007c34725313

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