Remove _ASTROPY_SETUP_

[larrybradley]

Followup to #338

[codecov]

Codecov Report

Merging #339 (763a29a) into main (0087448) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #339      +/-   ##
==========================================
- Coverage   91.86%   91.86%   -0.01%     
==========================================
  Files          33       33              
  Lines        2508     2507       -1     
==========================================
- Hits         2304     2303       -1     
  Misses        204      204              

Impacted Files	Coverage Δ
regions/__init__.py	100.00% <100.00%> (ø)

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