Updated tk-maya to v0.13.7

Release notes: https://github.com/shotgunsoftware/tk-maya/releases/tag/v0.13.7

Author: toolkitty

env/includes/common/engines.yml

@@ -22,7 +22,7 @@ common.engines.tk-houdini.location:
 common.engines.tk-maya.location:
   type: app_store
   name: tk-maya
-  version: v0.13.6
+  version: v0.13.7
 common.engines.tk-nuke.location:
   type: app_store
   name: tk-nuke