Update for Flutter 3.10 beta (#1746)

## Pre-launch Checklist

- [x] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [x] I signed the [CLA].
- [x] I read the [Contributors Guide].
- [x] I updated/added relevant documentation (doc comments with `///`).
- [ ] All existing and new tests are passing.

---------

Co-authored-by: David Iglesias <ditman@gmail.com>
Co-authored-by: Mark Thompson <2554588+MarkTechson@users.noreply.github.com>
Co-authored-by: John Ryan <ryjohn@google.com>

code_sharing/client/lib/main.dart

@@ -109,9 +109,9 @@ class _MyHomePageState extends State<MyHomePage> {
             ),
             if (isWriting) ...[
               const SizedBox(height: 10),
-              Row(
+              const Row(
                 mainAxisAlignment: MainAxisAlignment.center,
-                children: const <Widget>[
+                children: <Widget>[
                   Text(
                     'Communicating with server...',
                     style: TextStyle(fontSize: 32, color: Colors.blue),

code_sharing/client/pubspec.yaml

@@ -4,7 +4,7 @@ publish_to: "none"
 version: 1.0.0+1
 
 environment:
-  sdk: '>=2.19.5 <4.0.0'
+  sdk: ^3.0.0-0
 
 dependencies:
   cupertino_icons: ^1.0.2

code_sharing/server/pubspec.yaml

@@ -4,7 +4,7 @@ version: 1.0.0
 publish_to: "none"
 
 environment:
-  sdk: '>=2.19.5 <4.0.0'
+  sdk: ^3.0.0-0
 
 dependencies:
   args: ^2.0.0

code_sharing/shared/pubspec.yaml

@@ -3,7 +3,7 @@ description: Common data models required by our client and server
 version: 1.0.0
 
 environment:
-  sdk: '>=2.19.5 <4.0.0'
+  sdk: ^3.0.0-0
 
 dependencies:
   freezed_annotation: ^2.1.0