refactor: Support the generated images horizontal tiling display

--story=1017907 --user=刘瑞斌 【越秀农牧】图片生成节点，生成的图片，希望可以支持横向平铺展示 https://www.tapd.cn/57709429/s/1659636

Author: liuruibin

apps/application/flow/step_node/image_generate_step_node/impl/base_image_generate_node.py

@@ -47,7 +47,7 @@ def execute(self, model_id, prompt, negative_prompt, dialogue_number, dialogue_t
             file_url = FileSerializer(data={'file': file, 'meta': meta}).upload()
             file_urls.append(file_url)
         self.context['image_list'] = [{'file_id': path.split('/')[-1], 'url': path} for path in file_urls]
-        answer = '\n'.join([f"![Image]({path})" for path in file_urls])
+        answer = ' '.join([f"![Image]({path})" for path in file_urls])
         return NodeResult({'answer': answer, 'chat_model': tti_model, 'message_list': message_list,
                            'image': [{'file_id': path.split('/')[-1], 'url': path} for path in file_urls],
                            'history_message': history_message, 'question': question}, {})