Tox runs in CI not using pytest-rich

[joshuadavidthomas]

Looks like the move to the dedicated module isn't configured correctly, seeing this error in CI:

file src/pytest_rich.py (for module pytest_rich) not found

CI logs for tox step (PyPy 3.7)

Run tox
  tox
  shell: /bin/bash -e {0}
  env:
    pythonLocation: /Users/runner/hostedtoolcache/PyPy/3.7.13/x64/bin
.package create: /Users/runner/work/pytest-rich/pytest-rich/.tox/.package
.package installdeps: setuptools>=4[2](https://github.com/nicoddemus/pytest-rich/actions/runs/3370221765/jobs/5590853441#step:5:2), setuptools-scm, wheel
file src/pytest_rich.py (for module pytest_rich) not found
warning: no previously-included files matching '__pycache__' found under directory '*'
warning: no previously-included files matching '*.py[co]' found under directory '*'
file src/pytest_rich.py (for module pytest_rich) not found
warning: no previously-included files matching '__pycache__' found under directory '*'
warning: no previously-included files matching '*.py[co]' found under directory '*'
pypy37 create: /Users/runner/work/pytest-rich/pytest-rich/.tox/pypy[3](https://github.com/nicoddemus/pytest-rich/actions/runs/3370221765/jobs/5590853441#step:5:3)7
tox: pypy37
  pypy37 installdeps: pytest
  pypy37 inst: /Users/runner/work/pytest-rich/pytest-rich/.tox/.tmp/package/1/pytest-rich-0.1.2.dev21+g[4](https://github.com/nicoddemus/pytest-rich/actions/runs/3370221765/jobs/5590853441#step:5:4)b60b43.tar.gz
  pypy37 installed: attrs==22.1.0,cffi==1.1[5](https://github.com/nicoddemus/pytest-rich/actions/runs/3370221765/jobs/5590853441#step:5:5).0,commonmark==0.9.1,exceptiongroup==1.0.0,greenlet==0.4.13,hpy==0.0.3,importlib-metadata==5.0.0,iniconfig==1.1.1,packaging==21.3,pluggy==1.0.0,Pygments==2.13.0,pyparsing==3.0.9,pytest==7.2.0,pytest-rich @ file:///Users/runner/work/pytest-rich/pytest-rich/.tox/.tmp/package/1/pytest-rich-0.1.2.dev21%2Bg4b[6](https://github.com/nicoddemus/pytest-rich/actions/runs/3370221765/jobs/5590853441#step:5:7)0b43.tar.gz,readline==6.2.4.1,rich==12.6.0,tomli==2.0.1,typing_extensions==4.4.0,zipp==3.10.0
  pypy3[7](https://github.com/nicoddemus/pytest-rich/actions/runs/3370221765/jobs/5590853441#step:5:8) run-test-pre: PYTHONHASHSEED='22541272[8](https://github.com/nicoddemus/pytest-rich/actions/runs/3370221765/jobs/5590853441#step:5:9)'
  pypy37 run-test: commands[0] | pytest --rich tests
  ============================= test session starts ==============================
  platform darwin -- Python 3.7.13[pypy-7.3.[9](https://github.com/nicoddemus/pytest-rich/actions/runs/3370221765/jobs/5590853441#step:5:10)-final], pytest-7.2.0, pluggy-1.0.0
  cachedir: .tox/pypy37/.pytest_cache
  rootdir: /Users/runner/work/pytest-rich/pytest-rich, configfile: pyproject.toml
  plugins: rich-0.1.2.dev21+g4b60b43
  collected 2 items
  
  tests/test_rich.py ..                                                    [[10](https://github.com/nicoddemus/pytest-rich/actions/runs/3370221765/jobs/5590853441#step:5:11)0%]
  
  ============================== 2 passed in 2.73s ===============================
___________________________________ summary ____________________________________
  pypy37: commands succeeded
  congratulations :)