Backport #3126 Remove Order constraint from Hash instance for SortedSet

[gagandeepkalra]

addresses #3143

[gagandeepkalra]

learned a lot of Scala with this one 😌

[codecov-io]

Codecov Report

Merging #3339 into scala_2.11 will decrease coverage by 0.03%.
The diff coverage is 42.85%.

@@              Coverage Diff               @@
##           scala_2.11    #3339      +/-   ##
==============================================
- Coverage       93.46%   93.42%   -0.04%     
==============================================
  Files             385      385              
  Lines            7162     7165       +3     
  Branches          197      191       -6     
==============================================
  Hits             6694     6694              
- Misses            468      471       +3

Impacted Files	Coverage Δ
core/src/main/scala/cats/instances/sortedSet.scala	85.71% <25%> (-2.53%)	⬇️
...ala/cats/kernel/instances/SortedSetInstances.scala	91.66% <66.66%> (-8.34%)	⬇️

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[travisbrown]

Works for me!