Link to the Swift.org security policy (#21)

### Motivation

This project currently falls under the Swift.org security policy, not the SSWG.

### Modifications

Update the SECURITY.md file to point to the Swift.org common security policy.

### Result

The security file points to the common security policy.

### Test Plan

No functional change.   CI continues to pass.

Author: euanh

SECURITY.md

@@ -1,43 +1,3 @@
-# Security
+# Swift Security Process
 
-This document specifies the security process for the SwiftContainerPlugin project.
-
-## Disclosures
-
-### Private Disclosure Process
-
-The SwiftContainerPlugin team asks that known and suspected vulnerabilities be privately
-and responsibly disclosed by emailing [[email protected]](mailto:[email protected])
-with the details usually included with bug reports.
-**Do not file a public issue.**
-
-#### When to report a vulnerability
-
-* You think you have discovered a potential security vulnerability in SwiftContainerPlugin or any of the SwiftContainerPlugin projects.
-* You are unsure how a vulnerability affects SwiftContainerPlugin or any of the SwiftContainerPlugin projects.
-
-#### What happens next?
-
-* A member of the team will acknowledge receipt of the report within 3
-  working days (United States). This may include a request for additional
-  information about reproducing the vulnerability.
-* We will privately inform the Swift Server Work Group ([SSWG][sswg]) of the
-  vulnerability within 10 days of the report as per their [security
-  guidelines][sswg-security].
-* Once we have identified a fix we may ask you to validate it. We aim to do this
-  within 30 days. In some cases this may not be possible, for example when the
-  vulnerability exists at the protocol level and the industry must coordinate on
-  the disclosure process.
-* If a CVE number is required, one will be requested from [MITRE][mitre]
-  providing you with full credit for the discovery.
-* We will decide on a planned release date and let you know when it is.
-* Prior to release, we will inform major dependents that a security-related
-  patch is impending.
-* Once the fix has been released we will publish a security advisory on GitHub
-  and the [SSWG][sswg] will announce the vulnerability on the [Swift
-  forums][swift-forums-sec].
-
-[sswg]: https://github.com/swift-server/sswg
-[sswg-security]: https://github.com/swift-server/sswg/blob/main/process/incubation.md#security-best-practices
-[swift-forums-sec]: https://forums.swift.org/c/server/security-updates/
-[mitre]: https://cveform.mitre.org/
+Please see our main process guide on [Swift.org](https://www.swift.org/support/security.html)