Compat with numpy 1.25 and doc compat with astropy v5.3

[pllim]

Description

This pull request fixes test failures with numpy 1.25 and astropy 5.3.

[github-actions]

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• Do the proposed changes actually accomplish desired goals?
• Do the proposed changes follow the STScI coding guidelines?
• Are tests added/updated as required? If so, do they follow the STScI testing guidelines?
• Are docs added/updated as required?
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[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.30 ⚠️

Comparison is base (11db7cf) 97.09% compared to head (353832d) 96.80%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #356      +/-   ##
==========================================
- Coverage   97.09%   96.80%   -0.30%     
==========================================
  Files          17       17              
  Lines        2032     2032              
==========================================
- Hits         1973     1967       -6     
- Misses         59       65       +6     

Impacted Files	Coverage Δ
synphot/utils.py	99.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

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