Updated tk-flame to v1.15.6

Release notes: https://github.com/shotgunsoftware/tk-flame/wiki/Release-Notes#v1156

Author: mathurf

env/includes/common/engines.yml

@@ -57,7 +57,7 @@ common.engines.tk-aftereffects.location:
 common.engines.tk-flame.location:
   type: app_store
   name: tk-flame
-  version: v1.15.5
+  version: v1.15.6
 
 # Alias
 common.engines.tk-alias.location: