Update peps/pep-0813.rst

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

Author: warsaw

peps/pep-0813.rst

@@ -82,7 +82,7 @@ A new argument to built-in ``print``
 Built-in :func:`print` takes a new optional argument, appended to the end of the argument list, called
 ``pretty``, which can take one of the following values:
 
-* ``None`` - the default. No pretty printing is invoked.  Fully backward compatible
+* ``None`` - the default. No pretty printing is invoked.  Fully backward compatible.
 * ``True`` - use a temporary instance of the :py:class:`python:pprint.PrettyPrinter` class to get a
   pretty representation of the object.
 * An instance with a ``pformat()`` method, which has the same signature as