Fix typo in argparse docs. (pythonGH-92691) (python#92731)

Author: thueringa

Doc/library/argparse.rst

@@ -501,7 +501,7 @@ disallowed.
 fromfile_prefix_chars
 ^^^^^^^^^^^^^^^^^^^^^
 
-Sometimes, for example when dealing with a particularly long argument lists, it
+Sometimes, for example when dealing with a particularly long argument list, it
 may make sense to keep the list of arguments in a file rather than typing it out
 at the command line.  If the ``fromfile_prefix_chars=`` argument is given to the
 :class:`ArgumentParser` constructor, then arguments that start with any of the