Remove the pending deprecation warning for achromatic gaussian beams

[bhazelton]

Description

Remove the deprecation warning on using sigma to define gaussian beams. Analytic beams will move to pyuvdata soon and will retain this functionality, so no deprecation is needed.

Motivation and Context

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Reference simulation update or replacement
• Documentation change (documentation changes only)
• Version change
• Build or continuous integration change

Checklist:

For all pull requests:

• I have read the contribution guide.
• My code follows the code style of this project.

Documentation change checklist:

• Any updated docstrings use the numpy docstring format.
• If this is a significant change to the readme or other docs, I have checked that they are rendered properly on ReadTheDocs. (you may need help to get this branch to build on RTD, just ask!)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (3fcdb14) 99.50% compared to head (48f999a) 99.50%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #441      +/-   ##
==========================================
- Coverage   99.50%   99.50%   -0.01%     
==========================================
  Files          12       12              
  Lines        2210     2208       -2     
==========================================
- Hits         2199     2197       -2     
  Misses         11       11              

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[jpober]

@bhazelton review is complete, but the changelog has a conflict. If you can update, I can re-approve

[bhazelton]

@jpober done, thanks!

[bhazelton]

@jpober sorry, I had to make a couple more fixes because of pytest 8 dropping. It was actually good, it pointed to some warnings filters I'd missed. I also discovered some things I'd missed in #442, so I fixed those too.