Update flutter.dev links to more permanent locations

Author: parlough

pkgs/dart_services/README.md

@@ -15,8 +15,8 @@ information, code formatting, and quick fixes for issues.
 
 ### Initialize Flutter
 
-The Flutter SDK needs to be downloaded and setup; see
-https://docs.flutter.dev/get-started/install.
+The Flutter SDK needs to be downloaded and setup; check out
+https://flutter.dev/get-started.
 
 ### Running
 

pkgs/dartpad_ui/lib/main.dart

@@ -1080,7 +1080,7 @@ class OverflowMenu extends StatelessWidget {
   static const _menuItems = [
     (
       label: 'Install SDK',
-      uri: 'https://docs.flutter.dev/get-started/install',
+      uri: 'https://flutter.dev/get-started',
     ),
     (
       label: 'Sharing guide',

pkgs/dartpad_ui/lib/samples.g.dart

@@ -6,7 +6,7 @@
 /// built using the Flame game engine for Flutter.
 ///
 /// To learn how to build a more complete version of this game yourself,
-/// check out the codelab at https://docs.flutter.dev/brick-breaker.
+/// check out the codelab at https://flutter.dev/to/brick-breaker.
 library;
 
 import 'dart:async';