docs(magic-pdf): update model directory reference in configuration

Update the instruction in README_Ubuntu_CUDA_Acceleration_zh_CN.md to reference
the correct section number for downloading the model weights. This change ensures
that users are directed to the correct location in the document for setting up the
model directory in the magic-pdf.json configuration.

docs/README_Ubuntu_CUDA_Acceleration_zh_CN.md

@@ -68,7 +68,7 @@ pip install magic-pdf[full] detectron2 --extra-index-url https://wheels.myhloli.
 cp magic-pdf.template.json ~/magic-pdf.json
 ```
 
-在用户目录中找到magic-pdf.json文件并配置"models-dir"为[2. 下载模型权重文件](#2-下载模型权重文件)中下载的模型权重文件所在目录
+在用户目录中找到magic-pdf.json文件并配置"models-dir"为[7. 下载模型](#7-下载模型)中下载的模型权重文件所在目录
 > ❗️务必正确配置模型权重文件所在目录，否则会因为找不到模型文件而导致程序无法运行
 > 
 > windows系统中应把路径中所有的"\\"替换为"/",否则会因为转义原因导致json文件语法错误。