[WIP][DNM]: try to fix some bad RBI error suppressions

[jamieQ]

No description provided.

[jamieQ]

@swift-ci please smoke test macos

[gottesmm]

@jamieQ what test case are you looking to fix?

[jamieQ]

@swift-ci please smoke test macos

[jamieQ]

@gottesmm there are a number of outstanding issues filed that seem related to this, e.g. things like:

open class NS {
  func use() {}
}

@MainActor
func send(_ ns: sending NS) {
  Task.detached { ns.use() }
}

@MainActor
func badSend() async {
  let ns = NS()
  send(ns)
  ns.use()
}

I have a pending forum post with more info.