Cleanup: Update description of BKE_id_is_editable.

Getting the owner ID of an embedded liboverride is not that expansive
anymore.

Also explain difference between this function and the new similar
`ID_IS_EDITABLE` macro.

source/blender/blenkernel/BKE_lib_id.hh

@@ -747,12 +747,8 @@ ID *BKE_id_owner_get(ID *id, const bool debug_relationship_assert = true);
 /**
  * Check if that ID can be considered as editable from a high-level (editor) perspective.
  *
- * NOTE: This used to be done with a check on whether ID was linked or not, but now with system
- * overrides this is not enough anymore.
- *
- * NOTE: Execution of this function can be somewhat expensive currently. If this becomes an issue,
- * we should either cache that status info also in virtual override IDs, or address the
- * long-standing TODO of getting an efficient 'owner_id' access for all embedded ID types.
+ * \note Unlike the #ID_IS_EDITABLE macro, this also take into account higher-level aspects, e.g.
+ * it checks if the given ID is a system overrides (which should not be editable from the UI).
  */
 bool BKE_id_is_editable(const Main *bmain, const ID *id);