You have 2 ways to disable it.
One just for one app, and one global.
For one app : sudo nano /etc/nginx/conf.d/my-domain/my-application.conf
There you can comment the line importing the import :
# show YunoHost panel access
#include conf.d/yunohost_panel.conf.inc;
Finally restart nginx sudo service ngnix reload
If you want to globally disable it :
comment everything in /etc/nginx/conf.d/yunohost_panel.conf.inc
So each app will continue to import it, but it will be empty (only comments), so nothing will happen.