Make new method final

[travisbrown]

This is a minor thing to follow up on #3423, which introduces two new toNev methods but only makes one of them final. There are a lot of places where we missed the boat on making things final, and can't now because of bincompat, but for new methods like this I think we should try to do it consistently.

[codecov-commenter]

Codecov Report

Merging #3429 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3429   +/-   ##
=======================================
  Coverage   91.64%   91.64%           
=======================================
  Files         381      381           
  Lines        8268     8268           
  Branches      225      227    +2     
=======================================
  Hits         7577     7577           
  Misses        691      691           

Flag	Coverage Δ
#scala_version_212	91.63% <ø> (ø)
#scala_version_213	91.41% <ø> (-0.03%)	⬇️

Impacted Files	Coverage Δ
core/src/main/scala/cats/data/NonEmptyList.scala	98.74% <ø> (ø)

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[saraiva132]

NonEmptyList is a final class so there is no need for its methods to be final.

LazyNonEmptyList is not a final class. Perhaps there could be some considerations into making it final which would remove the need for its methods to be final (I believe most of them are but some are not).

[travisbrown]

@saraiva132 Ah, thanks, I missed that! Agreed, it's not needed here.

[saraiva132]

Np @travisbrown