Remove a Site from Web Notifications in Microsoft Edge

1. Open the Microsoft Edge app.

2. Click/tap on the Settings and more (Alt+X) button at the top right corner, and click/tap on Settings. 
3. Click/tap on Advanced on the left side, and click/tap on the Manage permissions button under Website permissions on the right side. 
4. Perform the following actions below for what you would like to do:

To Remove All Sites from Web Notifications in Microsoft Edge

Click/tap on Clear all. (see screenshot below)

To Remove a Single Site from Web Notifications in Microsoft Edge

Hover the pointer on the site you want to remove, and click/tap on the clear X button to the right of it. (see screenshot below)