Prefer RooParametricHist in test

[nsmith-]

We could also use cmscombine conda package in tests to avoid the warning

[nsmith-]

 =============================== warnings summary ===============================
tests/test_rhalphalib.py::test_rhalphabet
  /home/runner/work/rhalphalib/rhalphalib/.nox/tests-python-3-9-root-6-22-08/lib/python3.9/site-packages/rhalphalib/function.py:285: UserWarning: BernsteinPoly is deprecated. Consider switching to BasisPoly(..., basis='Bernstein', ...)
    warnings.warn("BernsteinPoly is deprecated. Consider switching to BasisPoly(..., basis='Bernstein', ...)")

tests/test_rhalphalib.py::test_rhalphabet
tests/test_rhalphalib.py::test_monojet
  /home/runner/work/rhalphalib/rhalphalib/.nox/tests-python-3-9-root-6-22-08/lib/python3.9/site-packages/rhalphalib/sample.py:676: RuntimeWarning: Could not load RooParametricHist, falling back to RooParametricStepFunction, which has strange rounding issues.
  Set ParametericSample.PreferRooParametricHist = False to disable this warning
    warnings.warn(

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
======================== 2 passed, 3 warnings in 38.81s ========================

[nsmith-]

I think for now it's probably fine to have that warning in the CI test. We could remove it by running CI with cmscombine conda package installed to provide RooParametricHist

[rkansal47]

LGTM. Got rid of the first warning, now:

=============================== warnings summary ===============================
tests/test_rhalphalib.py::test_rhalphabet
tests/test_rhalphalib.py::test_monojet
  /home/runner/work/rhalphalib/rhalphalib/.nox/tests-python-3-9-root-6-22-08/lib/python3.9/site-packages/rhalphalib/sample.py:676: RuntimeWarning: Could not load RooParametricHist, falling back to RooParametricStepFunction, which has strange rounding issues.
  Set ParametericSample.PreferRooParametricHist = False to disable this warning
    warnings.warn(

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
======================== 2 passed, 2 warnings in 35.96s ========================