Update URL in Code of Conduct (#11224)

Author: Redth

.github/CODE_OF_CONDUCT.md

@@ -3,4 +3,4 @@
 This project has adopted the code of conduct defined by the Contributor Covenant
 to clarify expected behavior in our community.
 
-For more information, see the [.NET Foundation Code of Conduct](https://dotnetfoundation.org/code-of-conduct).
+For more information, see the [.NET Foundation Code of Conduct](https://dotnetfoundation.org/about/policies/code-of-conduct).