MAINT: cycle ops tests

[jklenzing]

Description

Updates ops environment tests to use python 3.9.

Code still supports 3.6, but there is no way of testing this. A partial list of things to do to update the code is documented in #245.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

GitHub Actions

Checklist:

• [rc] Make sure you are merging into the develop (not main) branch
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• Add a note to CHANGELOG.md, summarizing the changes
• Update zenodo.json file for new code contributors

If this is a release PR, replace the first item of the above checklist with the release
checklist on the wiki: https://github.com/pysat/pysat/wiki/Checklist-for-Release