Fix for issue #2237: do not cache results that cannot be parsed.

[mkelley]

Address #2237 by catching result parse errors and removing the corresponding cached file, if applicable. Also add a mock test to that effect.

[codecov]

Codecov Report

Merging #2253 (55d6619) into main (17c79f9) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #2253      +/-   ##
==========================================
+ Coverage   62.40%   62.44%   +0.03%     
==========================================
  Files         131      131              
  Lines       16777    16785       +8     
==========================================
+ Hits        10470    10481      +11     
+ Misses       6307     6304       -3     

Impacted Files	Coverage Δ
astroquery/jplhorizons/core.py	66.34% <100.00%> (+1.85%)	⬆️

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[bsipocz]

Thanks @mkelley!