Update changelog

Author: dopey

CHANGELOG.md

@@ -48,6 +48,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
   from certificate requests in certificate templates (smallstep/crypto#767)
 - Allow to specify audience when generating JWK provisioner tokens (smallstep/certificates#2326)
 - Add SSH certificate type to exposed metrics (smallstep/certificates#2290)
+- Enable dynamic validation of project ownership within a GCP organization
+  when using the GCP Cloud Instance Identity provisioner (smallstep/certificates#2133)
 
 ### Changed