refactor: remove unused imports and redundant test node creation in controller_init_test

Author: pavanpodila

packages/vyuh_node_flow/test/unit/controller/controller_init_test.dart

@@ -9,7 +9,6 @@
 @Tags(['unit'])
 library;
 
-import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:vyuh_node_flow/vyuh_node_flow.dart';
 
@@ -286,10 +285,6 @@ void main() {
         id: 'node-1',
         position: const Offset(10, 20),
       );
-      final node2 = createTestNode(
-        id: 'node-2',
-        position: const Offset(30, 40),
-      );
 
       // Constructor initialization
       final constructorController = NodeFlowController<String>(nodes: [node1]);