I don't know how and why I find the following in my robots.txt
Sitemap: http://www.[mySite].com/magento2/sitemap.xml
worse the link opens to a "404 page not found".
I have tried to remove it from my robots.txt (under Stores\General\General\Design) but just the next day and I can see it down at the end of my http://www.[mySite].com/sitemap.xml
Note that at the top of my http://www.[mySite].com/magento2/sitemap.xml there is a correct link to my sitemap.
How can I remove that permanently?