Astropy updates 2023.07

[mkelley]

Currently supported astropy is >=4.3. Remove code branches for astropy < 4. Remove commented out reference to a deprecated astropy method.

[codecov[bot]]

Codecov Report

Merging #381 (3966709) into main (fc90ec0) will increase coverage by 0.03%. The diff coverage is 60.00%.

@@            Coverage Diff             @@
##             main     #381      +/-   ##
==========================================
+ Coverage   76.80%   76.84%   +0.03%     
==========================================
  Files          78       78              
  Lines        6984     6974      -10     
==========================================
- Hits         5364     5359       -5     
+ Misses       1620     1615       -5     

Impacted Files	Coverage Δ
sbpy/conftest.py	85.71% <50.00%> (+12.03%)	:arrow_up:
sbpy/activity/dust.py	99.15% <100.00%> (+1.57%)	:arrow_up:

[jianyangli]

@mkelley can you give me some context for this PR? I remember seeing a relevant message from someone astropy, but didn't keep track of it. Thanks.

[mkelley]

This address issue #372, and simplifies the Afrho/Efrho code.

[mkelley]

And removes some code from the testing setup in conftest.py Since we do not support astropy < 4.3, none of these lines are executed in our tests, which is why the coverage is increased by this PR.

[jianyangli]

Thanks Mike. All looks good to me. I also linked this PR with issue #372 if that's OK with you.

[mkelley]

Perfect!