use Github's vulnerability reporting

Signed-off-by: Marina Moore <[email protected]>

docs/SECURITY.md

@@ -8,7 +8,8 @@ You may report issues for the most recent version of go-tuf. We will not retroac
 
 ## Reporting a Vulnerability
 
-If you discover a potential security issue in this project we ask that you notify the go-tuf maintainers via our [vulnerability reporting form](https://forms.gle/ShM4s3mLbUAx5QHo8). At the minimum, the report must contain the following:
+If you discover a potential security issue in this project we ask that you notify the go-tuf maintainers via [Github's private reporting feature](https://docs.github.com/en/code-security/security-advisories/guidance-on-reporting-and-writing/privately-reporting-a-security-vulnerability). At the minimum, the report must contain the following:
+
 * A description of the issue.
 * A specific version or commit SHA of `go-tuf` where the issue reproduces.
 * Instructions to reproduce the issue.