HEROKU_SLUG_COMMIT is deprecated and should use HEROKU_BUILD_COMMIT

[jasonkarns]

Per heroku: https://devcenter.heroku.com/articles/dyno-metadata#dyno-metadata

The commit hash for the current release. This field is deprecated. Use HEROKU_BUILD_COMMIT instead

[linear]

PY-2089

[ericapisani]

Hi @jasonkarns ,

I've pulled this into our backlog, thanks for letting us know!