Updated tk-framework-desktopserver to v1.6.4

Release notes: https://github.com/shotgunsoftware/tk-framework-desktopserver/wiki/Release-Notes#v164

Author: toolkitty

env/includes/common/frameworks.yml

@@ -44,7 +44,7 @@ frameworks:
       name: tk-framework-widget
   tk-framework-desktopserver_v1.x.x:
     location:
-      version: v1.6.3
+      version: v1.6.4
       type: app_store
       name: tk-framework-desktopserver
   tk-framework-desktopclient_v0.x.x: