Deprecate the usage of XENONnT/ax_env

[dachengx]

What is the problem / what does the code in this PR do

Use base_environment for pytest, following XENONnT/base_environment#1487.

WFSim needs you:

• Please add a test for this PR, as a bare minimum, make sure it's covered in coveralls!
• Can you add a docsting to all your functions?

Pay attention:

• Due to databases being needed for testing, making a PR from your own fork will typically NOT run the tests. If you then merge master might break

[coveralls]

coverage: 82.67% (-0.1%) from 82.78%
when pulling d079c05 on update_test
into 8180bda on master.