docs: clarify scalar index config normalization

Author: ddupg

lance_ray/index.py

@@ -228,9 +228,9 @@ def _normalize_distributed_scalar_index_type(
 ) -> tuple[str, str | IndexConfig]:
     """Return the logical type and worker input for a distributed scalar index.
 
-    ``IndexConfig`` is a Core plugin configuration, whose type names are lowercase.
-    Keep the caller-owned configuration immutable while normalizing its type.  FTS is
-    a public alias for Core's ``inverted`` plugin.
+    Keep the caller-owned configuration immutable while normalizing its type for the
+    worker.  ``IndexConfig`` plugin names are normalized to lowercase; FTS is a
+    public alias for Core's ``inverted`` plugin.
     """
     if isinstance(index_type, str):
         logical_index_type = index_type.upper()