Sign in to the Azure portal using the Global administrator account .
Select Azure Active Directory, select Company branding, and then select Configure.
In the Advanced settings section,
Switch the “Show option to remain signed in” setting to No.
The Stay signed in? option is now hidden and will not appear when the user sign in.
From this moment on the user must sign in each time the browser is closed and reopened.
More info :
https://docs.microsoft.com/en-us/azure/active-directory/fundamentals/keep-me-signed-in