fix size in prepare_write_resolved_requires_ent
fix size in prepare_write_resolved_requires_ent

Summary:
i recently made `prepare_write_typed_parse_ents` take an optional `resolved_requires` arg and call this `prepare_write_resolved_requires_ent`, instead of hardcoding `None`.

it calculates the size incorrectly: the header size should be included when it writes resolved requires. this didn't break anything because we only call it with `Some` from the saved state codepath, where we had an extra `header_size` making up for it.

Changelog: [internal]

Reviewed By: samwgoldman

Differential Revision: D40435175

fbshipit-source-id: 78f532b59dccf8d109b4a8a9a05499d46ce05ea7

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