Update to Scala.js 0.6.16

[fthomas]

No description provided.

[fthomas]

Thanks to scala-js/scala-js#2908 this allows to delete our own def nextAfter(start: Float, direction: Double): Float.

[codecov-io]

Codecov Report

Merging #279 into master will decrease coverage by 2.21%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #279      +/-   ##
==========================================
- Coverage   99.29%   97.07%   -2.22%     
==========================================
  Files          36       35       -1     
  Lines         424      410      -14     
  Branches       18        3      -15     
==========================================
- Hits          421      398      -23     
- Misses          3       12       +9

Impacted Files	Coverage Δ
.../eu/timepit/refined/scalacheck/util/Adjacent.scala	100% <100%> (ø)	⬆️

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