Docs: Fix SOURCE_URI (#118945)

Doc/tools/extensions/pyspecific.py

@@ -33,7 +33,7 @@
 ISSUE_URI = 'https://bugs.python.org/issue?@action=redirect&bpo=%s'
 GH_ISSUE_URI = 'https://github.com/python/cpython/issues/%s'
 # Used in conf.py and updated here by python/release-tools/run_release.py
-SOURCE_URI = 'https://github.com/python/cpython/tree/3.13/%s'
+SOURCE_URI = 'https://github.com/python/cpython/tree/main/%s'
 
 # monkey-patch reST parser to disable alphabetic and roman enumerated lists
 from docutils.parsers.rst.states import Body