We normally recommend that access token lifetimes be kept as short as is practical for your application, and use silent authentication to get new access tokens when the current one expires to avoid degrading the UX with additional login requests.
This way, when permissions are changed, they will only be out of sync for the lifetime of their access token.
That being said, you can use the option ignoreCache to force a network call on the getTokenSilently call: https://auth0.github.io/auth0-spa-js/interfaces/gettokensilentlyoptions.html - this should fetch a new token even if the current one has not yet expired.