Add latest changes from gitlab-org/security/gitlab@12-7-stable-ee

CHANGELOG-EE.md

 Please view this file on the master branch, on stable branches it's out of date.
+## 12.7.3
+
+- No changes.
+
 ## 12.7.2
 - No changes.

VERSION

-12.7.3
+12.7.3-ee