Simplify @pyside_cache decorator

This fixes a compatibility issue with Python 3.9+, and at the same time
avoids a not-yet-quite-stable area of Blender's Python API.

blender_cloud/blender.py

@@ -47,7 +47,7 @@ log = logging.getLogger(__name__)
 icons = None
 
 
-@pyside_cache("version")
+@pyside_cache
 def blender_syncable_versions(self, context):
     """Returns the list of items used by SyncStatusProperties.version EnumProperty."""
 
@@ -117,7 +117,7 @@ class SyncStatusProperties(PropertyGroup):
         self["available_blender_versions"] = new_versions
 
 
-@pyside_cache("project")
+@pyside_cache
 def bcloud_available_projects(self, context):
     """Returns the list of items used by BlenderCloudProjectGroup.project EnumProperty."""