Replace deprecated numpy trapezoid/trapz usage with scipy trapezoid

[djhoese]

This PR completes the removal of deprecated trapz/np.trapezoid usage. It also sets the lower bound of the scipy dependency to 1.6.0 where trapz was renamed to trapezoid.

• Closes Deprecate old scipy and remove use of trapz (numpy and scipy) #229
• Tests added
• Tests passed: Passes pytest pyspectral
• Passes flake8 pyspectral
• Fully documented
• Add your name to AUTHORS.md if not there already

[codecov]

Codecov Report

Attention: Patch coverage is 72.72727% with 3 lines in your changes missing coverage. Please review.

Project coverage is 90.25%. Comparing base (d6b5c58) to head (af71f1e).
Report is 5 commits behind head on main.

Files	Patch %	Lines
pyspectral/solar.py	40.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #233      +/-   ##
==========================================
+ Coverage   90.20%   90.25%   +0.05%     
==========================================
  Files          23       22       -1     
  Lines        2521     2515       -6     
==========================================
- Hits         2274     2270       -4     
+ Misses        247      245       -2     

Flag	Coverage Δ
unittests	90.25% <72.72%> (+0.05%)	⬆️

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[djhoese]

Adam and I had talked about the distutils change on slack and needing to release it. This is a similar change where numpy and scipy have both deprecated the "trapz" function in favor of "trapezoid" naming, but numpy is also suggesting people import and use scipy directly (one referenced the other, but my understanding it is all just scipy now).