This is a Tampermonkey user script which dismisses notifications sent from GitHub Environment's "Required reviewers" feature:
Once the notifications page (https://github.com/notifications) loads, the script will select the relevant visible notifications then dismiss them as a batch. If you have many pages of these, you'll need to refresh the page to trigger the script again.
To install, copy the script's contents into Tampermonkey after hitting "Create a new script" or you can import it from the raw text GitHub URL.
There is an open discussion with GitHub to natively support silencing these notifications though it's been lingering for a while.