all subdir in docs will have ipynb files, not only 'pratices'. (#4106)

as the script will remove the ipynb files after converting, so the `Edit On Github` function will be misled.

ci_scripts/hooks/pre-doc-compile.sh

@@ -29,7 +29,7 @@ done
 
 ## 2 convert all ipynb files to markdown, and delete the ipynb files.
 # ../practices/**/*.ipynb
-for i in ${SCRIPT_DIR}/../../docs/practices/**/*.ipynb ; do
+for i in $(find ${SCRIPT_DIR}/../../docs/ -name '*.ipynb' -type f ) ; do
     echo "convert $i to markdown and delete ipynb"
     jupyter nbconvert --to markdown "$i"
     rm "$i"