Nnbd docs updates for various widgets (#72389)

packages/flutter/lib/src/widgets/drag_target.dart

@@ -105,7 +105,7 @@ enum DragAnchor {
 ///
 /// {@youtube 560 315 https://www.youtube.com/watch?v=QzA4c4QHZCY}
 ///
-/// {@tool dartpad --template=stateful_widget_scaffold_no_null_safety}
+/// {@tool dartpad --template=stateful_widget_scaffold}
 ///
 /// The following example has a [Draggable] widget along with a [DragTarget]
 /// in a row demonstrating an incremented `acceptedData` integer value when

packages/flutter/lib/src/widgets/inherited_notifier.dart

@@ -28,7 +28,7 @@ import 'framework.dart';
 /// changed. When it returns true, the dependents are marked as needing to be
 /// rebuilt this frame.
 ///
-/// {@tool dartpad --template=stateful_widget_material_ticker_no_null_safety}
+/// {@tool dartpad --template=stateful_widget_material_ticker}
 ///
 /// This example shows three spinning squares that use the value of the notifier
 /// on an ancestor [InheritedNotifier] (`SpinModel`) to give them their
@@ -50,13 +50,13 @@ import 'framework.dart';
 /// ```dart preamble
 /// class SpinModel extends InheritedNotifier<AnimationController> {
 ///   SpinModel({
-///     Key key,
-///     AnimationController notifier,
-///     Widget child,
+///     Key? key,
+///     AnimationController? notifier,
+///     required Widget child,
 ///   }) : super(key: key, notifier: notifier, child: child);
 ///
 ///   static double of(BuildContext context) {
-///     return context.dependOnInheritedWidgetOfExactType<SpinModel>().notifier.value;
+///     return context.dependOnInheritedWidgetOfExactType<SpinModel>()!.notifier!.value;
 ///   }
 /// }
 ///
@@ -81,7 +81,7 @@ import 'framework.dart';
 /// ```
 ///
 /// ```dart
-/// AnimationController _controller;
+/// late AnimationController _controller;
 ///
 /// @override
 /// void initState() {

packages/flutter/lib/src/widgets/notification_listener.dart

@@ -17,7 +17,7 @@ import 'framework.dart';
 
 typedef NotificationListenerCallback<T extends Notification> = bool Function(T notification);
 
-/// {@tool dartpad --template=stateless_widget_material_no_null_safety}
+/// {@tool dartpad --template=stateless_widget_material}
 ///
 /// This example shows a [NotificationListener] widget
 /// that listens for [ScrollNotification] notifications. When a scroll

packages/flutter/lib/src/widgets/overscroll_indicator.dart

@@ -46,7 +46,7 @@ import 'ticker_provider.dart';
 /// [OverscrollIndicatorNotification.paintOffset] to the
 /// notification, or use a [NestedScrollView].
 ///
-/// {@tool dartpad --template=stateless_widget_scaffold_no_null_safety}
+/// {@tool dartpad --template=stateless_widget_scaffold}
 ///
 /// This example demonstrates how to use a [NotificationListener] to manipulate
 /// the placement of a [GlowingOverscrollIndicator] when building a
@@ -81,7 +81,7 @@ import 'ticker_provider.dart';
 /// ```
 /// {@end-tool}
 ///
-/// {@tool dartpad --template=stateless_widget_scaffold_no_null_safety}
+/// {@tool dartpad --template=stateless_widget_scaffold}
 ///
 /// This example demonstrates how to use a [NestedScrollView] to manipulate the
 /// placement of a [GlowingOverscrollIndicator] when building a

packages/flutter/lib/src/widgets/shortcuts.dart

@@ -386,7 +386,7 @@ class ShortcutManager extends ChangeNotifier with Diagnosticable {
 /// when invoking an [Action] via a keyboard key combination that maps to an
 /// [Intent].
 ///
-/// {@tool dartpad --template=stateful_widget_scaffold_center_no_null_safety}
+/// {@tool dartpad --template=stateful_widget_scaffold_center}
 ///
 /// Here, we will use a [Shortcuts] and [Actions] widget to add and remove from a counter.
 /// This can be done by creating a child widget that is focused and pressing the logical key

packages/flutter/lib/src/widgets/table.dart

@@ -81,7 +81,7 @@ class _TableElementRow {
 ///
 /// {@youtube 560 315 https://www.youtube.com/watch?v=_lbE0wsVZSw}
 ///
-/// {@tool dartpad --template=stateless_widget_scaffold_no_null_safety}
+/// {@tool dartpad --template=stateless_widget_scaffold}
 ///
 /// This sample shows a `Table` with borders, multiple types of column widths and different vertical cell alignments.
 ///