[Concurrency] Remove experimental @task macro

In order to avoid confusion about it in 6.2, we should remove this.
We can revisit and bring it back in the future if necessary

Author: ktoso

lib/Macros/Sources/SwiftMacros/CMakeLists.txt

@@ -14,7 +14,6 @@ add_swift_macro_library(SwiftMacros
   OptionSetMacro.swift
   DebugDescriptionMacro.swift
   DistributedResolvableMacro.swift
-  TaskMacro.swift
   SyntaxExtensions.swift
   TaskLocalMacro.swift
   SwiftifyImportMacro.swift

lib/Macros/Sources/SwiftMacros/SyntaxExtensions.swift

@@ -43,17 +43,4 @@ extension ImplicitlyUnwrappedOptionalTypeSyntax {
       trailingTrivia: self.trailingTrivia
     )
   }
-}
-
-extension LabeledExprListSyntax {
-  /// Retrieve the first element with the given label.
-  func first(labeled name: String) -> Element? {
-    return first { element in
-      if let label = element.label, label.text == name {
-        return true
-      }
-
-      return false
-    }
-  }
-}
+}

lib/Macros/Sources/SwiftMacros/TaskMacro.swift

@@ -1902,18 +1902,6 @@ ExpandBodyMacroRequest::evaluate(Evaluator &evaluator,
         if (bufferID)
           return;
 
-        // '@Task' is gated behind the 'ConcurrencySyntaxSugar'
-        // experimental feature.
-        if (macro->getParentModule()->getName().is("_Concurrency") &&
-            macro->getBaseIdentifier().is("Task") &&
-            !ctx.LangOpts.hasFeature(Feature::ConcurrencySyntaxSugar)) {
-          ctx.Diags.diagnose(
-              customAttr->getLocation(),
-              diag::experimental_macro,
-              macro->getName());
-          return;
-        }
-
         SourceFile * macroSourceFile = nullptr;
         if (auto *fnDecl = fn.getAbstractFunctionDecl()) {
           macroSourceFile = ::evaluateAttachedMacro(

lib/Sema/TypeCheckMacros.cpp

@@ -99,27 +99,6 @@ internal func _enqueueOnMain(_ job: UnownedJob)
 @freestanding(expression)
 public macro isolation<T>() -> T = Builtin.IsolationMacro
 
-/// Wrap the function body in a new top-level task on behalf of the
-/// given actor.
-@available(SwiftStdlib 5.1, *)
-@attached(body)
-public macro Task(
-  on actor: any GlobalActor,
-  name: String? = nil,
-  priority: TaskPriority? = nil
-) =
-  #externalMacro(module: "SwiftMacros", type: "TaskMacro")
-
-/// Wrap the function body in a new top-level task on behalf of the
-/// current actor.
-@available(SwiftStdlib 5.1, *)
-@attached(body)
-public macro Task(
-  name: String? = nil,
-  priority: TaskPriority? = nil
-) =
-  #externalMacro(module: "SwiftMacros", type: "TaskMacro")
-
 #endif
 
 #if $IsolatedAny