doc/sphinx/requirements.txt: Bump certifi and urllib3

As reported by GitHub dependabot, both of these packages should be
bumped to their latest versions to address security issues (neither of
which has a CVE assigned).

Reported-by: GitHub dependabot
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
1 file changed