Clean up doc comments for task APIs.

Cherry pick swiftlang#38815, b9dde85.

Author: amartini51

stdlib/public/Concurrency/Executor.swift

@@ -12,13 +12,13 @@
 
 import Swift
 
-/// A service which can execute jobs.
+/// A service that can execute jobs.
 @available(SwiftStdlib 5.5, *)
 public protocol Executor: AnyObject, Sendable {
   func enqueue(_ job: UnownedJob)
 }
 
-/// A service which can execute jobs.
+/// A service that executes jobs.
 @available(SwiftStdlib 5.5, *)
 public protocol SerialExecutor: Executor {
   // This requirement is repeated here as a non-override so that we

stdlib/public/Concurrency/GlobalActor.swift

@@ -15,12 +15,12 @@ import Swift
 /// A type that represents a globally-unique actor that can be used to isolate
 /// various declarations anywhere in the program.
 ///
-/// A type that conforms to the `GlobalActor` protocol and is marked with the
+/// A type that conforms to the `GlobalActor` protocol and is marked with
 /// the `@globalActor` attribute can be used as a custom attribute. Such types
 /// are called global actor types, and can be applied to any declaration to
 /// specify that such types are isolated to that global actor type. When using
 /// such a declaration from another actor (or from nonisolated code),
-/// synchronization is performed through the \c shared actor instance to ensure
+/// synchronization is performed through the shared actor instance to ensure
 /// mutually-exclusive access to the declaration.
 @available(SwiftStdlib 5.5, *)
 public protocol GlobalActor {

stdlib/public/Concurrency/Task.swift

@@ -44,7 +44,10 @@ public func withTaskCancellationHandler<T>(
 
 @available(SwiftStdlib 5.5, *)
 extension Task {
-  /// Returns `true` if the task is cancelled, and should stop executing.
+  /// A Boolean value that indicates whether the task should stop executing.
+  ///
+  /// After the value of this property becomes `true`, it remains `true` indefinitely.
+  /// There is no way to uncancel a task.
   ///
   /// - SeeAlso: `checkCancellation()`
   public var isCancelled: Bool {
@@ -60,10 +63,10 @@ extension Task {
 
 @available(SwiftStdlib 5.5, *)
 extension Task where Success == Never, Failure == Never {
-  /// Returns `true` if the task is cancelled, and should stop executing.
+  /// A Boolean value that indicates whether the task should stop executing.
   ///
-  /// If no current `Task` is available, returns `false`, as outside of a task
-  /// context no task cancellation may be observed.
+  /// After the value of this property becomes `true`, it remains `true` indefinitely.
+  /// There is no way to uncancel a task.
   ///
   /// - SeeAlso: `checkCancellation()`
   public static var isCancelled: Bool {
@@ -75,7 +78,7 @@ extension Task where Success == Never, Failure == Never {
 
 @available(SwiftStdlib 5.5, *)
 extension Task where Success == Never, Failure == Never {
-  /// Check if the task is cancelled and throw an `CancellationError` if it was.
+  /// Throws an error if the task was canceled.
   ///
   /// The error is always an instance of `Task.CancellationError`.
   ///
@@ -87,10 +90,10 @@ extension Task where Success == Never, Failure == Never {
   }
 }
 
-/// The default cancellation thrown when a task is cancelled.
+/// An error that indicates a task was canceled.
 ///
 /// This error is also thrown automatically by `Task.checkCancellation()`,
-/// if the current task has been cancelled.
+/// if the current task has been canceled.
 @available(SwiftStdlib 5.5, *)
 public struct CancellationError: Error {
   // no extra information, cancellation is intended to be light-weight