Switch from PyMongo ssl config to tls config

[adrianclay]

Why

PyMongo 4 changed how this config should be specified.

https://pymongo.readthedocs.io/en/4.8.0/examples/tls.html

Type of change

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

Checklist:

• I have performed a self-review of my code
• 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
• I have updated the Changelog with details of my change in the UNRELEASED section if this change will affect end users

[adrianclay]

PR #159 would have caught this defect if it were merged, as it fails the build if the Adaptors are unable to boot up.