Remove useless Order constraint in NonEmptyMap constructors

[Kambius]

Constructors which take SortedMap as a parameter don't need to take extra Order implicit as it is already there.

[johnynek]

If we have released with this it breaks binary compatibility. Otherwise looks good.

[Kambius]

@johnynek yes, but it's not a big deal to fix client code with this changes. NonEmptyMap isn't used widely so maybe we could break binary compatibility? What other options we have if it's not the case?

[LukaJCB]

The other option is to wait until 2.0 unfortunately :/

[larsrh]

Couldn't the same hack apply here as elsewhere? Duplicate the methods and mark them as private[cats]?

[diesalbla]

@LukaJCB Was this Pull Request applied on a different form? The cats 2.0 already came.

[diesalbla]

Would it work to introduce a binary-compatible yet deprecated method, which used no implicits for the Order paramter, but which would generate the same bytecode-level, uncurrified method?

  def fromMap[K, A](as: SortedMap[K, A], k: Order[K]): Option[NonEmptyMap[K, A]] = 
    this.fromMap(as)

[joroKr21]

Superseded by #3473