You don’t. You must wait for Google to renew their keys and for an update.
The important message is:
The following signatures were invalid: EXPKEYSIG 1397BC53640DB551 Google Inc. (Linux Packages Signing Authority)
It means that the cryptographic signature is invalid. The source of this can be an attack, a misconfiguration, or other kind of technical problem. Forcing your system to update will result in running an unverified version of your web browser, which can expose you to a lot of security troubles.