Improve wording

Co-authored-by: Cody Maloney <cmaloney@users.noreply.github.com>

Author: hugovk

peps/pep-0387.rst

@@ -150,7 +150,7 @@ several releases:
    Depending on the degree of incompatibility, this could be on
    `Discourse <https://discuss.python.org/>`__,
    the `issue tracker <https://github.com/python/cpython/issues/>`__,
-   or the appropriate workgroup or SIG.
+   or in an appropriate workgroup or SIG.
    If the discussion reaches consensus a :pep:`PEP <1>` or
    similar document may be written.
    Hopefully users of the affected API will pipe up to comment.