docs: Notifications REST API missing `security_advisory_credit` reason

[setchy]

Code of Conduct

• I have read and agree to the GitHub Docs project's Code of Conduct

What article on docs.github.com is affected?

https://docs.github.com/en/rest/activity/notifications?apiVersion=2022-11-28

What part(s) of the article would you like to see updated?

Add the reason security_advisory_credit

Additional information

[nguyenalex836]

@setchy Thank you for opening an issue and linking it to your PR! ✨