Remove redundant final modifiers on objects

[travisbrown]

Similar to #3182. Dotty is complaining about these finals on objects and they're unnecessary on Scala 2.

[LukaJCB]

👍

[codecov-io]

Codecov Report

Merging #3183 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3183   +/-   ##
=======================================
  Coverage   92.99%   92.99%           
=======================================
  Files         376      376           
  Lines        7381     7381           
  Branches      195      195           
=======================================
  Hits         6864     6864           
  Misses        517      517

Flag	Coverage Δ
#scala_version_212	93.32% <ø> (ø)	⬆️
#scala_version_213	90.59% <ø> (+0.01%)	⬆️

Impacted Files	Coverage Δ
core/src/main/scala/cats/data/Chain.scala	98.43% <ø> (ø)	⬆️
kernel/src/main/scala/cats/kernel/Comparison.scala	100% <ø> (ø)	⬆️

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