Correct minor grammar mistake (GH-15404)

Doc/library/json.rst

@@ -129,7 +129,7 @@ See :ref:`json-commandline` for detailed documentation.
    inputs and outputs were typically scrambled unless
    :class:`collections.OrderedDict` was specifically requested.  Starting
    with Python 3.7, the regular :class:`dict` became order preserving, so
-   it is no longer necessary specify :class:`collections.OrderedDict` for
+   it is no longer necessary to specify :class:`collections.OrderedDict` for
    JSON generation and parsing.