Correct the joinus.png location
diff --git a/doc/doc_ch/joinus.PNG b/doc/doc_ch/joinus.PNG
deleted file mode 100644
index cd9de9c14b..0000000000
Binary files a/doc/doc_ch/joinus.PNG and /dev/null differ
diff --git a/doc/joinus.PNG b/doc/joinus.PNG
index b8724a9b0a..cd9de9c14b 100644
Binary files a/doc/joinus.PNG and b/doc/joinus.PNG differ

Correct the joinus.png location