chore: fix lints.

Signed-off-by: Sahil Kumar <xdsahil@gmail.com>

packages/stream_chat/lib/src/client/client.dart

@@ -1696,7 +1696,7 @@ class ClientState {
   void updateUsers(List<User?> userList) {
     final newUsers = {
       ...users,
-      for (var user in userList)
+      for (final user in userList)
         if (user != null) user.id: user,
     };
     _usersController.add(newUsers);

packages/stream_chat/test/src/client/client_test.dart

@@ -975,7 +975,7 @@ void main() {
         // skipping initial seed event -> {} users
         client.state.usersStream.skip(1),
         emitsInOrder([
-          {for (var user in users) user.id: user},
+          {for (final user in users) user.id: user},
         ]),
       );