Fix typo: cunked -> chunked

Author: ChiragAgg5k

templates/flutter/lib/src/client.dart.twig

@@ -9,7 +9,7 @@ import 'upload_progress.dart';
 ///
 /// The [Client] is also responsible for managing user's sessions.
 abstract class Client {
-  /// The size for cunked uploads in bytes.
+  /// The size for chunked uploads in bytes.
   static const int chunkSize = 5 * 1024 * 1024;
 
   /// Holds configuration such as project.