fix doc COMPILE_CN.md

doc/COMPILE_CN.md

@@ -174,7 +174,7 @@ make -j10
 mkdir app-build && cd app-build
 cmake -DPYTHON_INCLUDE_DIR=$PYTHON_INCLUDE_DIR \
     -DPYTHON_LIBRARIES=$PYTHON_LIBRARIES \
-    -DPYTHON_EXECUTABLE=$PYTHON_EXECUTABLE \    
+    -DPYTHON_EXECUTABLE=$PYTHON_EXECUTABLE \
     -DAPP=ON ..
 make
 ```