Revert update advanced guide (#1876)

* update_fluiddoc_1.7_0303,test=develop

* update_advanced_guide_0304,test=develop

* revert_update_advanced_guide,test=develop

doc/fluid/advanced_guide/index_cn.rst

@@ -16,7 +16,7 @@
 
     - `二次开发 <../advanced_guide/addon_development/index_cn.html>`_ ：介绍如何新增Operator和如何向飞桨开源社区贡献代码
 
-    - `环境变量FLAGS <../advanced_guide/flags/index_cn.html>`_ 
+    - `环境变量FLAGS <../advanced_guide/flags/flags_cn.html>`_ 
 
 
 ..  toctree::

doc/fluid/advanced_guide/index_en.rst

@@ -20,7 +20,7 @@ So far you have already been familiar with PaddlePaddle. And the next expectatio
 
     - `Addon Development <addon_development/index_en.html>`_ ：How to contribute codes and documentation to our communities
 
-    - `FLAGS <flasgs/flags_en.html>`_ 
+    - `FLAGS <flags/flags_en.html>`_ 
 
 
 ..  toctree::