Fix bounds on floating point range testing (JuliaLang#48561)

* Fix bounds on floating point range testing

Follow up on JuliaLang#48465.

Addresses CI failure noted here JuliaLang#48465 (comment).

* Use simpler error bound

test/ranges.jl

@@ -887,7 +887,15 @@ function range_fuzztests(::Type{T}, niter, nrange) where {T}
  @test m == length(r)
  @test strt == first(r)
  @test Δ == step(r)
- @test stop ≈ last(r) atol = eps((n-1)*Δ) + eps(stop) # account for intermediate rounding in computation of stop
+ # potential floating point error:
+ # stop = strt + (n-1)*Δ
+ # * error <= eps((n-1)*Δ)/2 <= abs((n-1)*Δ)/2 * eps(T)
+ # + error <= eps(stop)/2 <= abs(stop)/2 * eps(T)
+ # last(r)
+ # rat(strt) error <= eps(strt)/2 <= abs(strt)/2 * eps(T)
+ # rat(Δ) error <= (n-1)*eps(Δ)/2 <= abs((n-1)*Δ)/2 * eps(T)
+ # T(...) error <= eps(last(r))/2 <= abs(stop)/2 * eps(T)
+ @test stop ≈ last(r) atol = (abs(strt)/2 + (n-1)*abs(Δ) + abs(stop)) * eps(T)
  l = range(strt, stop=stop, length=n)
  @test n == length(l)
  @test strt == first(l)