Fix edge and spectrum type in xas client

[munrojm]

Fixes issues with edge and spectrum_type not getting formatted correctly in the GET request when using the generic search method in the XASRester.

[codecov-commenter]

Codecov Report

Merging #619 (05b8d2c) into main (250f51c) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #619      +/-   ##
==========================================
+ Coverage   91.68%   91.69%   +0.01%     
==========================================
  Files          35       35              
  Lines        1479     1481       +2     
==========================================
+ Hits         1356     1358       +2     
  Misses        123      123              

Impacted Files	Coverage Δ
src/mp_api/routes/xas.py	93.54% <100.00%> (+0.44%)	⬆️

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