Fix/replace incorrent "racePair derives race" law

[alexandru]

Unfortunately I introduced an incorrect law for race.

The problem in cats-effect's test is that the IOs aren't non-deterministic enough and we can't fix it unless we introduce a Timer in Arbitrary[IO].

This problem was caught by Monix's tests for Task, because Arbitrary[Task] does generate tasks with arbitrary time delays.

So this law is incorrect because it expects a deterministic result and the whole point of race is precisely its non-determinism.

[codecov-io]

Codecov Report

Merging #142 into master will decrease coverage by 0.13%.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##           master     #142      +/-   ##
==========================================
- Coverage   90.11%   89.97%   -0.14%     
==========================================
  Files          47       47              
  Lines         971      978       +7     
  Branches       82       82              
==========================================
+ Hits          875      880       +5     
- Misses         96       98       +2

[LukaJCB]

LGTM! :)

[alexandru]

Thanks @LukaJCB for the review, merged as I'd like another hash release.