bpo-40439: Update broken link in lexical analysis docs (GH-20184)

Automerge-Triggered-By: @csabella

Author: Akarys42

Doc/reference/lexical_analysis.rst

@@ -325,7 +325,7 @@ of identifiers is based on NFKC.
 
 A non-normative HTML file listing all valid identifier characters for Unicode
 4.1 can be found at
-https://www.dcl.hpi.uni-potsdam.de/home/loewis/table-3131.html.
+https://www.unicode.org/Public/13.0.0/ucd/DerivedCoreProperties.txt
 
 
 .. _keywords: