Google has started sending out messages with the subject:
[Action Advised] Inactive registered OAuth URIs for your project(s) will be removed from Google Developer Console by July 12, 2021, for non-compliance with URI validation rules
And the leader:
If you’re here, the URLs are likely referencing your Discourse site and this is your Google Login integration.
At the bottom of the email are details specific to your project such as:
If this project is unused (e.g. the site no longer exists), it can be deleted.
If the URL has changed since the project was set up and the old URL is unused, that URL can be deleted.
If the URL is http-only, it will need to be changed to https (as per the requirements linked above).
If it’s another case, feel free to ask about it here.