swift

f88d8a49 - [Concurrency] Fix preconcurrency downgrade behavior for Sendable closures.

[Concurrency] Fix preconcurrency downgrade behavior for Sendable closures. Sendable violations inside `@preconcurrency @Sendable` closures should be suppressed in minimal checking, and diagnosed as warnings under complete checking, including the Swift 6 language mode. (cherry picked from commit d2d317a3d7afdb57745c74a272c98f5e5512d998)