Removed dangling `since Python` at the end of library/xml.rst. (GH-11201)

Doc/library/xml.rst

@@ -75,8 +75,8 @@ decompression bomb         Safe             Safe              Safe             S
 2. :mod:`xml.dom.minidom` doesn't expand external entities and simply returns
    the unexpanded entity verbatim.
 3. :mod:`xmlrpclib` doesn't expand external entities and omits them.
-4. Since Python 3.8.0, external general entities are no longer processed by
-   default since Python.
+4. Since Python 3.8, external general entities are no longer processed by
+   default.
 
 
 billion laughs / exponential entity expansion