Update candidates list after making a move

[sjsrey]

This addresses #201

[codecov]

Codecov Report

Merging #202 (33a1450) into main (dec0031) will increase coverage by 0.2%.
The diff coverage is 88.9%.

@@           Coverage Diff           @@
##            main    #202     +/-   ##
=======================================
+ Coverage   65.1%   65.3%   +0.2%     
=======================================
  Files         23      23             
  Lines       2458    2461      +3     
  Branches     494     494             
=======================================
+ Hits        1600    1607      +7     
+ Misses       786     777      -9     
- Partials      72      77      +5     

Impacted Files	Coverage Δ
spopt/region/region_k_means.py	97.3% <88.9%> (-1.3%)	⬇️
spopt/_version.py	33.8% <0.0%> (+1.5%)	⬆️