Recently Microsoft pushed out two new promo buttons for Project Online that encourage the user to try Project for the web, see below:
For a lot of organisations, this is no issue but for some they won’t want to expose these. Luckily Microsoft made it configurable in PWA Settings so that you can turn this off if you want. It is on by default but your PWA Admin will be able to turn it off if needed. To turn if off, access PWA Settings > Additional Server Settings and scroll down to the bottom of the page and uncheck the “Turn on exploration” checkbox seen below:
Click Save then those two new promo buttons will then be removed.
Modern Work Management - Project and the Power Platform blog 