Run a final docs build when EOL to add the banner

Author: hugovk

peps/pep-0101.rst

@@ -858,6 +858,8 @@ else does them.  Some of those tasks include:
 
   * review and dispose of open issues marked for this branch
 
+- Run a final build of the online docs to add the end-of-life banner
+
 - Announce the branch retirement in the usual places:
 
   * `discuss.python.org`_