`@Sendable` does not peer through typealiases

[compnerd]

typealias FType = (Int) -> Void
func f(_: @Sendable FType) {
}

This yields:

error: @Sendable attribute only applies to function types
func f(_: @Sendable FType) {
                    ^

[etcwilde]

Linked with: rdar://103716454

Thank you for the report.