Update py mongo to version 4.0

[SamuelNoB]

Proposed changes:

• update package PyMongo to version 4.0 so that it can run with MongoDB 5
• closes #10539

Status (please check what you already did):

• [ ] updated the documentation
• [ ] updated the changelog (please check changelog for instructions)
• [x] reformat files using black (please check Readme for instructions)

[CLAassistant]

All committers have signed the CLA.

[tmbo]

@SamuelNoB the PR contains merge conflicts. do you mind resolving them first before we review it?

[SamuelNoB]

@tmbo sure! I will resolve it as soon as possible

[lahdekorpi]

There seem to be a lot of breaking changes between PyMongo 3 and 4. As this commit only updates the dependency version number, have all the functionality been tested to work with the newer version?