Correct the type in doc comment for parameter.

Fixes rdar://79539036

Author: amartini51

stdlib/public/Concurrency/CheckedContinuation.swift

@@ -259,7 +259,7 @@ extension CheckedContinuation {
 ///   - function: A string identifying the declaration that is the notional
 ///     source for the continuation, used to identify the continuation in
 ///     runtime diagnostics related to misuse of this continuation.
-///   - body: A closure that takes an `UnsafeContinuation` parameter.
+///   - body: A closure that takes a `CheckedContinuation` parameter.
 ///     You must resume the continuation exactly once.
 @available(SwiftStdlib 5.5, *)
 public func withCheckedContinuation<T>(