Add Scaffold to Tooltip code samples (#69532)

packages/flutter/lib/src/material/tooltip.dart

@@ -30,7 +30,7 @@ import 'tooltip_theme.dart';
 ///
 /// {@youtube 560 315 https://www.youtube.com/watch?v=EeEfD5fI-5Q}
 ///
-/// {@tool dartpad --template=stateless_widget_material}
+/// {@tool dartpad --template=stateless_widget_scaffold_center}
 ///
 /// This example show a basic [Tooltip] which has a [Text] as child.
 /// [message] contains your label to be shown by the tooltip when
@@ -38,17 +38,15 @@ import 'tooltip_theme.dart';
 ///
 /// ```dart
 /// Widget build(BuildContext context) {
-///   return Center(
-///     child: Tooltip(
+///   return Tooltip(
 ///     message: "I am a Tooltip",
 ///     child: Text("Tap this text and hold down to show a tooltip."),
-///     ),
 ///   );
 /// }
 /// ```
 /// {@end-tool}
 ///
-/// {@tool dartpad --template=stateless_widget_material}
+/// {@tool dartpad --template=stateless_widget_scaffold_center}
 ///
 /// This example covers most of the attributes available in Tooltip.
 /// `decoration` has been used to give a gradient and borderRadius to Tooltip.
@@ -64,8 +62,7 @@ import 'tooltip_theme.dart';
 ///
 /// ```dart
 /// Widget build(BuildContext context) {
-///   return Center(
-///     child: Tooltip(
+///   return Tooltip(
 ///     message: "I am a Tooltip",
 ///     child: Text("Tap this text and hold down to show a tooltip."),
 ///     decoration: BoxDecoration(
@@ -80,7 +77,6 @@ import 'tooltip_theme.dart';
 ///     ),
 ///     showDuration: Duration(seconds: 2),
 ///     waitDuration: Duration(seconds: 1),
-///     ),
 ///   );
 /// }
 /// ```