allowing skipping recheck of direct_dependent_files
allowing skipping recheck of direct_dependent_files

Summary:
When stuff changes, `direct_dependent_files` contain files whose dependencies might have changed because of new / changed / deleted files. These files need their requires re-resolved and participate in updating the dependency graph.

But we don't always need to recheck them. If we need do, the signatures of their dependencies should change to indicate that we need to.

Unfortunately, by marking them in `recheck_map`, we block skipping these files during rechecks. IIRC this used to make sense when re-resolving requires used to be part of checking files. It became redundant when that part was split out.

This diff unblocks skipping these files during rechecks, by not marking them in `recheck_map`.

Reviewed By: samwgoldman

Differential Revision: D15193887

fbshipit-source-id: 6bd8bfa23aa7a6e56eac48eaef10359dc1b56123

gabelevi/flow,samwgoldman/flow,facebook/flow,samwgoldman/flow,gabelevi/flow,samwgoldman/flow,facebook/flow,samwgoldman/flow,mroch/flow,gabelevi/flow,facebook/flow,facebook/flow,samwgoldman/flow,gabelevi/flow,mroch/flow,mroch/flow,samwgoldman/flow,samwgoldman/flow,mroch/flow,mroch/flow,facebook/flow,facebook/flow,gabelevi/flow,gabelevi/flow,mroch/flow,mroch/flow,facebook/flow,gabelevi/flow