swift

57e259b6 - Remove an old, horrible compatibility hack in the _Concurrency module

Remove an old, horrible compatibility hack in the _Concurrency module The concurrency module was getting an implicit `-disable-availability-checking` as a workaround from the Swift 5.6 days. Remove it, because it causes problems with the new `Failure` type in the async for..in loop. Fixes a back-deployment issue with async algorithms in the _Concurrency library that use the async for..in loop.