Upgrade Pymongo throughout to resolve security notifications in dependabot

[stevenmccullaghmadetech]

What

Please include a summary of the changes and the related issue

Why

Please include details of the reasoning for these changes

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Internal change (non-breaking change with no effect on the functionality affecting end users)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

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]

This PR doesn't seem to address the source of the outdated Pymongo, which is a very old version of motor within the common module.

I propose we instead upgrade that, instead of adding an additional dependency on pymongo everywhere.

[stevenmccullaghmadetech]

@adrianclay Both the setup.py and Pipfile within the common module request motor 3.5.1 which is the latest tag of the repo you linked to and and the latest version here: https://pypi.org/project/motor/

[adrianclay]

In that case I wouldn't bother with trying to fix the Dependabot alert. It appears to be only relevant when connecting to an untrusted Mongo server.

Implemented.