Move SetKW files to the correct folder

[victorg1991]

With the project structure change, I missed moving SetKW files to the correct folder :(

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@29cc568). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master     #262   +/-   ##
=========================================
  Coverage          ?   42.15%           
  Complexity        ?      262           
=========================================
  Files             ?      138           
  Lines             ?     3141           
  Branches          ?      399           
=========================================
  Hits              ?     1324           
  Misses            ?     1691           
  Partials          ?      126

Impacted Files	Coverage Δ	Complexity Δ
...c/main/kotlin/kategory/instances/SetKWInstances.kt	0% <ø> (ø)	0 <0> (?)
...tegory-core/src/main/kotlin/kategory/data/SetKW.kt	91.66% <100%> (ø)	3 <0> (?)

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