Unfortunately I don't think this is possible at the moment.
In the future we should hopefully be able to use the Permissions API to check and revoke notifications (as well as other APIs like geolocation etc).
However, while we can currently query the status of a permission, the revoke method is unsupported. I believe it was possible in Firefox until recently, but in 51 the functionality was changed to default to off.
As per MDN:
The revoke() function has been disabled by default starting in Firefox
51, since its design has been brought into question in the Web
Applications Security Working Group. It can be re-enabled by setting
the preference dom.permissions.revoke.enable to true.
Example of permissions API:
navigator.permissions.query({name:'notifications'}).then(function(result) {
console.log(result);
});
Result is prompt/denied/granted. Change 'query' to 'revoke' for denying permissions.
navigator.permissions.revoke({name:'notifications'});
Alternatively, this answer from a couple of years ago suggests an alternate approach which you might find interesting - using localStorage to approximate this functionality.