chore: Update URL for the LinkedIn Security Key.

Author: chriseppstein

CONTRIBUTING.md

@@ -84,7 +84,7 @@ Tips for Getting Your Pull Request Accepted
    unlikely to be accepted. **You have been warned.**
 
 [disclosure_guidelines]: https://www.linkedin.com/help/linkedin/answer/62924
-[pubkey]: https://gist.github.com/chriseppstein/3f45d3a8e6fb42f24cb7b3f77f21381e
+[pubkey]: https://www.linkedin.com/help/linkedin/answer/79676
 [disclosure_email]: mailto:[email protected]?subject=Vulnerability%20in%20Github%20LinkedIn/css-blocks%20-%20%3Csummary%3E
 [WEBSITE]: ./packages/@css-blocks/website
 [PLAYGROUND]: ./packages/@css-blocks/playground