Fix CI badge in README (crewjam#555)

Author: brunograsselli

README.md

@@ -2,7 +2,7 @@
 
 [![](https://godoc.org/github.com/crewjam/saml?status.svg)](http://godoc.org/github.com/crewjam/saml)
 
-![Build Status](https://github.com/crewjam/saml/workflows/Presubmit/badge.svg)
+![Build Status](https://github.com/crewjam/saml/actions/workflows/test.yml/badge.svg)
 
 Package saml contains a partial implementation of the SAML standard in golang.
 SAML is a standard for identity federation, i.e. either allowing a third party to authenticate your users or allowing third parties to rely on us to authenticate their users.