This took me too long to figure out. I hope this helps you if you are googling around.
To force the GitHub Slack app to stop @ mentioning you. The only way I found is to do the following.
- In a separate slack workspace (that you don't care about/won't mention you), install the GitHub app
/github signinand login to your GitHub account
- This will break the connection in your original slack workspace, and you'll no longer be @ mentioned by the bot.
I hope your notifications are now less annoying.