remove comment about updating the parser module; we do not need to do that anymore (#26526)

Grammar/Grammar

 # Grammar for Python
 
-# Note:  Changing the grammar specified in this file will most likely
-#        require corresponding changes in the parser module
-#        (../Modules/parsermodule.c).  If you can't make the changes to
-#        that module yourself, please co-ordinate the required changes
-#        with someone who can; ask around on python-dev for help.  Fred
-#        Drake <fdrake@acm.org> will probably be listening there.
-
 # NOTE WELL: You should also follow all the steps listed at
 # https://docs.python.org/devguide/grammar.html