Updated tk-framework-shotgunutils to v5.8.8

Release notes: https://github.com/shotgunsoftware/tk-framework-shotgunutils/wiki/Release-Notes#v588

Author: toolkitty

env/includes/common/frameworks.yml

@@ -29,7 +29,7 @@ frameworks:
       name: tk-framework-shotgunutils
   tk-framework-shotgunutils_v5.x.x:
     location:
-      version: v5.8.7
+      version: v5.8.8
       type: app_store
       name: tk-framework-shotgunutils
   tk-framework-adminui_v0.x.x: