more precise type names in docs

Author: ktoso

stdlib/public/Concurrency/DiscardingTaskGroup.swift

@@ -506,11 +506,7 @@ public func withThrowingDiscardingTaskGroup<GroupResult>(
 /// use a ``DiscardingTaskGroup`` instead of a throwing one, or catch specific errors in
 /// operations submitted using `addTask`
 ///
-/// Since a `TaskGroup` is a structured concurrency primitive, cancellation is
-/// automatically propagated through all of its child-tasks (and their child
-/// tasks).
-///
-/// Since a `TaskGroup` is a structured concurrency primitive, cancellation is
+/// Since a `ThrowingDiscardingTaskGroup` is a structured concurrency primitive, cancellation is
 /// automatically propagated through all of its child-tasks (and their child
 /// tasks).
 ///

stdlib/public/Concurrency/TaskGroup.swift

@@ -563,7 +563,7 @@ extension TaskGroup: Sendable { }
 /// - when an error is thrown out of the `withThrowingTaskGroup(...) { }` closure,
 /// - when the ``Task`` running this task group is cancelled.
 ///
-/// Since a `TaskGroup` is a structured concurrency primitive, cancellation is
+/// Since a `ThrowingTaskGroup` is a structured concurrency primitive, cancellation is
 /// automatically propagated through all of its child-tasks (and their child
 /// tasks).
 ///