Remove misformatted exclamation marks in docs (#102694)

Remove the exclamation mark from :program:`!foo` in .rst files because
it inadvertently shows up in the rendered HTML.

(Sphinx's cross-referencing roles use a '!' prefix to suppress
hyperlinking[1], but :program: is not a cross-referencing role so the
'!' is displayed verbatim.)

The exclamation marks in venv.rst were introduced in #98350. See
comments [2] and [3] for additional discussion.

[1]: https://www.sphinx-doc.org/en/master/usage/restructuredtext/roles.html#cross-referencing-syntax
[2]: https://github.com/python/cpython/pull/98350#issuecomment-1285965759
[3]: https://github.com/python/cpython/pull/98350#issuecomment-1286394047

Reported-by: Vinay Sajip <vinay_sajip@yahoo.co.uk>