Advance minimum scipy to 1.6

~[ ] Closes #xxx~
~[ ] Added tests to cover all new or modified code.~
~[ ] Clearly documented all new API functions with PEP257 and numpydoc compliant docstrings.~
~[ ] Added new API functions to docs/api.rst.~
~[ ] Non-API functions clearly documented with docstrings or comments as necessary.~
[x] Adds description and name entries in the appropriate "what's new" file in docs/whatsnew for all changes. Includes link to the GitHub Issue with :issue:`num` or this Pull Request with :pull:`num`. Includes contributor name and/or GitHub username (link with :ghuser:`user`).
[x] Pull request is nearly complete and ready for detailed review.
[x] Maintainer: Appropriate GitHub Labels and Milestone are assigned to the Pull Request and linked Issue.

Recent CI runs show a deprecation warning from scipy: scipy.integrate.trapz is deprecated and replaced by scipy.integrate.trapezoid:

pvanalytics/tests/quality/test_irradiance.py: 24 warnings
  /opt/hostedtoolcache/Python/3.12.1/x64/lib/python3.12/site-packages/pandas/core/resample.py:450: DeprecationWarning: 'scipy.integrate.trapz' is deprecated in favour of 'scipy.integrate.trapezoid' and will be removed in SciPy 1.14.0
    func = lambda x: how(x, *args, **kwargs)

pvanalytics/tests/quality/test_irradiance.py::test_daily_insolation_limits_uneven
pvanalytics/tests/quality/test_irradiance.py::test_daily_insolation_limits_uneven
pvanalytics/tests/quality/test_irradiance.py::test_daily_insolation_limits_uneven
pvanalytics/tests/quality/test_irradiance.py::test_daily_insolation_limits_uneven
pvanalytics/tests/quality/test_irradiance.py::test_daily_insolation_limits_uneven
pvanalytics/tests/quality/test_irradiance.py::test_daily_insolation_limits_uneven
  /home/runner/work/pvanalytics/pvanalytics/pvanalytics/quality/irradiance.py:428: DeprecationWarning: 'scipy.integrate.trapz' is deprecated in favour of 'scipy.integrate.trapezoid' and will be removed in SciPy 1.14.0
    lambda day: integrate.trapz(y=day, x=hours[day.index])

We could work around the name change with try/except, but it's easiest to just increase our minimum scipy so that trapezoid is always available. Note that scipy 1.6.0 was released December 31, 2020.

pvlib / pvanalytics

Advance minimum scipy to 1.6 #205