Task_id to material_id in xas tests

[munrojm]

This fixes xas tests to accommodate change in query operators from task_id to material_id.

[codecov-commenter]

Codecov Report

Merging #366 (60bd03a) into main (903f78c) will decrease coverage by 0.04%.
The diff coverage is 80.00%.

@@            Coverage Diff             @@
##             main     #366      +/-   ##
==========================================
- Coverage   93.12%   93.08%   -0.05%     
==========================================
  Files          61       61              
  Lines        1965     1966       +1     
==========================================
  Hits         1830     1830              
- Misses        135      136       +1     

Impacted Files	Coverage Δ
src/mp_api/__init__.py	90.00% <75.00%> (-10.00%)	⬇️
src/mp_api/routes/xas/query_operators.py	100.00% <100.00%> (ø)

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[mkhorton]

Thanks @munrojm, apologies I missed this

[munrojm]

@mkhorton, no worries!