Break tox's passenv parameters into multiple lines

[peterallenwebb]

resolves #6421

Description

Break passenv into multiple lines to work with new version of tox

Checklist

• I have read the contributing guide and understand what's expected of me
• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• I have opened an issue to add/update docs, or docs changes are not required/relevant for this PR
• I have run changie new to create a changelog entry

After merge

• Close [CT-1643] [Bug] Deal with another change in tox behavior #6421 manually. Since this PR is a backport, the issue will not be resolved automatically upon merging.

[github-actions]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the contributing guide.

[MichelleArk]

@cla-bot check

[peterallenwebb]

resetting quality checks

[leahwicz]

@cla-bot check

[cla-bot]

The cla-bot has been summoned, and re-checked this pull request!