s/stringobject/bytesobject/ (closes #22036)

Patch by Martin Matusiak.
diff --git a/Objects/stringlib/README.txt b/Objects/stringlib/README.txt
index ab506d6..8ff6ad8 100644
--- a/Objects/stringlib/README.txt
+++ b/Objects/stringlib/README.txt
@@ -1,4 +1,4 @@
-bits shared by the stringobject and unicodeobject implementations (and
+bits shared by the bytesobject and unicodeobject implementations (and
 possibly other modules, in a not too distant future).
 
 the stuff in here is included into relevant places; see the individual