Update DiscardingTaskGroup.swift

Dear @amartini51 ,

I would like to correct the missing periods. However, I found you have the PR for that file. Have you ever mind to Co-Worker on swiftlang#75407 for correct this file?

Thanks,

Author: lamtrinhdev

stdlib/public/Concurrency/DiscardingTaskGroup.swift

@@ -1,4 +1,4 @@
-//===----------------------------------------------------------------------===//
+ //===----------------------------------------------------------------------===//
 //
 // This source file is part of the Swift.org open source project
 //
@@ -713,7 +713,7 @@ public func _unsafeInheritExecutor_withThrowingDiscardingTaskGroup<GroupResult>(
 /// however a discarding group cannot poll child tasks for results and therefore assumes that child
 /// task throws are an indication of a group wide failure. In order to avoid such behavior,
 /// use a ``DiscardingTaskGroup`` instead of a throwing one, or catch specific errors in
-/// operations submitted using `addTask`
+/// operations submitted using `addTask`.
 ///
 /// Since a `ThrowingDiscardingTaskGroup` is a structured concurrency primitive, cancellation is
 /// automatically propagated through all of its child-tasks (and their child