Update dependencies and fix lint issues in demos.

Author: rkistner

demos/supabase-anonymous-auth/pubspec.lock

@@ -34,7 +34,7 @@ class _LoginPageState extends State<LoginPage> {
       await Supabase.instance.client.auth.signInWithPassword(
           email: _usernameController.text, password: _passwordController.text);
 
-      if (mounted) {
+      if (context.mounted) {
         Navigator.of(context).pushReplacement(MaterialPageRoute(
           builder: (context) => homePage,
         ));

demos/supabase-edge-function-auth/lib/widgets/login_page.dart

@@ -34,7 +34,7 @@ class _SignupPageState extends State<SignupPage> {
       final response = await Supabase.instance.client.auth.signUp(
           email: _usernameController.text, password: _passwordController.text);
 
-      if (mounted) {
+      if (context.mounted) {
         if (response.session != null) {
           Navigator.of(context).pushReplacement(MaterialPageRoute(
             builder: (context) => homePage,