Fix array unwrapping in distinct

[shyamd]

This ensures the built-in distinct call properly unwraps arrays.

[codecov]

Codecov Report

Merging #335 (a60e12f) into master (1848830) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #335      +/-   ##
==========================================
+ Coverage   87.51%   87.52%   +0.01%     
==========================================
  Files          28       28              
  Lines        2170     2172       +2     
==========================================
+ Hits         1899     1901       +2     
  Misses        271      271              

Impacted Files	Coverage Δ
src/maggma/stores/mongolike.py	82.57% <100.00%> (+0.14%)	⬆️

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