include circleci config in venv cache key

[graingert-coef]

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## Description of changes

Pre-Merge checklist

• [ ] The project was correctly built with npm run build.
• [ ] If there was any conflict, it was solved correctly.
• [ ] All changes were documented in CHANGELOG.md.
• [ ] All tests on CircleCI have passed.
• [ ] All Percy visual changes have been approved.
• [ ] Two people have :dancer:'d the pull request. You can be one of these people if you are a Dash Deck core contributor.

Reference Issues

Closes #[issue number]

Other comments

[graingert-coef]

CI is failing with https://app.circleci.com/pipelines/github/plotly/dash-deck/70/workflows/81c8c7c7-ae31-4f2c-a1d8-c335ed4c4410/jobs/226?utm_campaign=vcs-integration-link&utm_medium=referral&utm_source=github-checks-link&utm_content=summary Error: [Errno 2] No such file or directory: '/home/circleci/project/venv/bin/python' again so I'm going to try busting the cache