Fix tests

[AreWeDreaming]

Pins + fixes to get regression to pass again on master.

[AreWeDreaming]

I cannot reproduce this error locally.

[AreWeDreaming]

Using pip I can reproduce this!

[AreWeDreaming]

While I can reproduce this now the error is very confusing even with the debugger. The floating point colors come from the matplotlib.rcparams. The strangest part is that if I test this with same matplotlib version but in a pure conda environment then I don't get this bug.
Since our primary use-case for OMAS is to map DIII-D data which needs MDSplus, I'd say we change the CI/CD to install the environment through conda. This has some downstream consequences since omas is distributed on PyPi and then propagated to conda from there (as far as I remember).