Update scalafmt to 2.6.3

[regadas]

Closes #449
Closes #451

[codecov-commenter]

Codecov Report

Merging #452 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop     #452   +/-   ##
========================================
  Coverage    91.69%   91.69%           
========================================
  Files           42       42           
  Lines         1396     1396           
  Branches        35       35           
========================================
  Hits          1280     1280           
  Misses         116      116           

Impacted Files	Coverage Δ
.../main/scala/com/twitter/chill/ClosureCleaner.scala	97.22% <ø> (ø)
...cala/com/twitter/chill/ScalaKryoInstantiator.scala	99.26% <ø> (ø)

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