Alter test workflow so the tests match the installed version

[znichollscr]

Description

If you don't do this, the tests can fail because tests from main will be used to check an old version. That isn't what we want this workflow to test. We want this workflow to test that installing from PyPI/conda leads to a correct installation.

Checklist

Please confirm that this pull request has done the following:

• [ ] Tests added (N/A)
• [x] Documentation added (where applicable)
• [x] Changelog item added to changelog/