Remove TaskGroup backDeployed annotation typo that included * (swiftlang#74756)

Fix typo on a single task group backDeployed annotation.

Author: ktoso

stdlib/public/Concurrency/TaskGroup.swift

@@ -64,7 +64,7 @@ import Swift
 /// For tasks that need to handle cancellation by throwing an error,
 /// use the `withThrowingTaskGroup(of:returning:body:)` method instead.
 @available(SwiftStdlib 5.1, *)
-@backDeployed(before: SwiftStdlib 6.0, *)
+@backDeployed(before: SwiftStdlib 6.0)
 @inlinable
 public func withTaskGroup<ChildTaskResult, GroupResult>(
   of childTaskResultType: ChildTaskResult.Type,