Replace enzyme with React Testing Library

[feanil]

This is part of openedx/public-engineering#195 (Enzyme Replacement)

The above ticket explains why but given that we want this to continue to work with the latest version of the openedx platform. We should make this migration in this repository as well.

[feanil]

@openedx/committers-cookie-policy-banner can one of you take on this work or otherwise schedule it to be done before the Sumac cut?

[feanil]

Looking at the repo though, it looks like this repo is already running tests with Node 18 so I wonder if the tests have all moved but we just haven't gotten around to removing the old dependency.