Update changelog-3.15.adoc

Author: mouligno

pages/apim/3.x/changelog/changelog-3.15.adoc

@@ -30,7 +30,7 @@ For upgrade instructions, please refer to https://docs.gravitee.io/apim/3.x/apim
 === Console
 
 - [Policy XSLT] Prevent usage of external XML DTD
-- Add a default value in the HTTP Methods field of Dynamic Dictionaries and Properties
+- Add a default value in the HTTP Methods field of Dynamic Dictionaries and Properties https://github.com/gravitee-io/issues/issues/8631[#8631]