python: update help text for check-tox

python: update help text for check-tox

Move it up near the check-pipenv help text, and update it to suggest parity.

(At the time I first added it, I wasn't sure if I would be keeping it,
but I've come to appreciate it as it has actually helped uncover bugs I
would not have noticed without it. It should stay.)

Signed-off-by: John Snow <[email protected]>
Reviewed-by: Willian Rampazzo <[email protected]>
Reviewed-by: Wainer dos Santos Moschetta <[email protected]>
Message-id: 20210629214323.1329806[email protected]
Signed-off-by: John Snow <[email protected]>