update changelog

CHANGELOG

 v7.13.1
   - Fix: user could steal specific runner
+  - Fix: don't send notifications for jobs with allow_failure set
+  - Fix invalid link to doc.gitlab.com
 v7.13.0
   - Allow to specify image and services in yml that can be used with docker
@@ -269,4 +271,4 @@ v1.2.0
 v1.1.0
   - Added JSON response for builds status
-  - Compatible with GitLab v4.0.0
+  - Compatible with GitLab v4.0.0
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