fix error in StepRange documentation

[udohjeremiah]

The doc says:

help?> StepRange

  StepRange{T, S} <: OrdinalRange{T, S}

  Ranges with elements of type T with spacing of type S. The step between each
  element is constant, and the range is defined in terms of a start and stop of
  type T and a step of type S. Neither T nor S should be floating point types. The
  syntax a:b:c with b > 1 and a, b, and c all integers creates a StepRange.

The part where it says:

The syntax a : b : c with b > 1 and a, b, and c all integers creates a StepRange.

is very misleading and confusing because b = 1 creates a StepRange:

julia> typeof(1:1:5)
StepRange{Int64, Int64}

And even b < 1 creates a StepRange as well:

julia> typeof(5:-1:1)
StepRange{Int64, Int64}

julia> collect(5:-1:1)
5-element Vector{Int64}:
 5
 4
 3
 2
 1

So I think the intended action of that word is to say: "zero as a step is not allowed.". If that's not it, then the b>0 or b!= 0 part can just be removed all together since the error message even tells that:

julia> 1:0:5
ERROR: ArgumentError: step cannot be zero

[LilithHafner]

Thanks!