[deps] revert the recent rev of package:ffi
[deps] revert the recent rev of package:ffi

Change-Id: Iaa7007876646e54461192c6072cc0621f66843cc
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/248921
Commit-Queue: Devon Carew <e996497f4f2225f0ee7a9f4d1696ee710b488b66@google.com>
Reviewed-by: Brian Quinlan <2ba0baab12cbdc73959f1aa8397b55b4d7de9371@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk