As mentioned by @matthew-shwery, you can not change the permission.
the best you could do is check for the permission and notify the user is the permission is denied
navigator.permissions.query({
name: 'geolocation'
}).then(function(result) {
if (result.state == 'granted') {
report(result.state);
geoBtn.style.display = 'none';
} else if (result.state == 'prompt') {
report(result.state);
geoBtn.style.display = 'none';
navigator.geolocation.getCurrentPosition(revealPosition, positionDenied, geoSettings);
} else if (result.state == 'denied') {
report(result.state);
geoBtn.style.display = 'inline';
}
result.onchange = function() {
report(result.state);
}
});
Geolocation docs