Reverts to previous releases of tk-shell and tk-shotgun.

QA shows the changes to Qt made in those engines caused problems with publish2.

Author: Jeff Beeland

env/includes/common/engines.yml

@@ -57,12 +57,12 @@ common.engines.tk-desktop.location:
 common.engines.tk-shell.location:
     type: app_store
     name: tk-shell
-    version: v0.5.2
+    version: v0.5.1
 
 # shotgun
 common.engines.tk-shotgun.location:
     type: app_store
     name: tk-shotgun
-    version: v0.5.3
+    version: v0.5.2