tests: Added coverage for unique items in array test

[jtyoung84]

There is an astronomically small chance the coverage will miss. I can try to seed the random number generator to provide 100% consistency.

[codecov-commenter]

Codecov Report

Merging #32 (0a5febd) into main (bdd9985) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main      #32   +/-   ##
=======================================
  Coverage   99.51%   99.51%           
=======================================
  Files          14       14           
  Lines         409      414    +5     
=======================================
+ Hits          407      412    +5     
  Misses          2        2           

Impacted Files	Coverage Δ
src/jsf/schema_types/array.py	100.00% <100.00%> (ø)

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