Fix more bincompat breakage

[travisbrown]

Fixes #3202 and all related issues I was able to turn up.

[codecov-io]

Codecov Report

Merging #3203 into master will decrease coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #3203      +/-   ##
==========================================
- Coverage   93.06%   93.05%   -0.02%     
==========================================
  Files         376      376              
  Lines        7409     7412       +3     
  Branches      198      192       -6     
==========================================
+ Hits         6895     6897       +2     
- Misses        514      515       +1

Flag	Coverage Δ
#scala_version_212	93.38% <100%> (-0.02%)	⬇️
#scala_version_213	92.82% <100%> (-0.02%)	⬇️

Impacted Files	Coverage Δ
core/src/main/scala/cats/instances/sortedSet.scala	83.33% <100%> (-2.39%)	⬇️
laws/src/main/scala/cats/laws/MonadErrorLaws.scala	100% <100%> (ø)	⬆️

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[travisbrown]

@kailuowang I added a comment about the overrides. What do you think?

[kailuowang]

Thanks!