Cleanup: LibOverride: Update comment.

source/blender/blenkernel/intern/lib_override.c

@@ -1922,7 +1922,9 @@ ID *BKE_lib_override_library_operations_store_start(Main *bmain,
                                                     ID *local)
 {
   if (ID_IS_OVERRIDE_LIBRARY_TEMPLATE(local) || ID_IS_OVERRIDE_LIBRARY_VIRTUAL(local)) {
-    /* This is actually purely local data with an override template, nothing to do here! */
+    /* This is actually purely local data with an override template, or one of those embedded IDs
+     * (root node trees, master collections or shapekeys) that cannot have their own override.
+     * Nothing to do here! */
     return NULL;
   }