Refactor: Get asset data via asset representation, not file

The "active_file" context member as a way to get the active asset should be
avoided, in favor of "asset". This moves us away from the file browser backend
as basis of the asset system,

scripts/modules/bpy_extras/asset_utils.py

@@ -25,11 +25,6 @@ class SpaceAssetInfo:
     def is_asset_browser_poll(cls, context: Context):
         return cls.is_asset_browser(context.space_data)
 
-    @classmethod
-    def get_active_asset(cls, context: Context):
-        if active_file := getattr(context, "active_file", None):
-            return active_file.asset_data
-
 
 class AssetBrowserPanel:
     bl_space_type = 'FILE_BROWSER'