argparse docs: normalize constant references (GH-98765)

(cherry picked from commit b27b57c)

Co-authored-by: Skip Montanaro <[email protected]>

Author: miss-islington

Doc/library/argparse.rst

@@ -63,7 +63,7 @@ Name                   Description
 action_                Specify how an argument should be handled                   ``'store'``, ``'store_const'``, ``'store_true'``, ``'append'``, ``'append_const'``, ``'count'``, ``'help'``, ``'version'``
 choices_               Limit values to a specific set of choices                   ``['foo', 'bar']``, ``range(1, 10)``, or :class:`~collections.abc.Container` instance
 const_                 Store a constant value
-default_               Default value used when an argument is not provided         Defaults to *None*
+default_               Default value used when an argument is not provided         Defaults to ``None``
 dest_                  Specify the attribute name used in the result namespace
 help_                  Help message for an argument
 metavar_               Alternate display name for the argument as shown in help
@@ -201,9 +201,10 @@ ArgumentParser objects
    * usage_ - The string describing the program usage (default: generated from
      arguments added to parser)
 
-   * description_ - Text to display before the argument help (default: none)
+   * description_ - Text to display before the argument help
+     (by default, no text)
 
-   * epilog_ - Text to display after the argument help (default: none)
+   * epilog_ - Text to display after the argument help (by default, no text)
 
    * parents_ - A list of :class:`ArgumentParser` objects whose arguments should
      also be included
@@ -1914,8 +1915,8 @@ FileType objects
       Namespace(out=<_io.TextIOWrapper name='file.txt' mode='w' encoding='UTF-8'>, raw=<_io.FileIO name='raw.dat' mode='wb'>)
 
    FileType objects understand the pseudo-argument ``'-'`` and automatically
-   convert this into ``sys.stdin`` for readable :class:`FileType` objects and
-   ``sys.stdout`` for writable :class:`FileType` objects::
+   convert this into :data:`sys.stdin` for readable :class:`FileType` objects and
+   :data:`sys.stdout` for writable :class:`FileType` objects::
 
       >>> parser = argparse.ArgumentParser()
       >>> parser.add_argument('infile', type=argparse.FileType('r'))