PI doc string needs updating

[eljfe]

Hi, Thanks for this package!

Small issue with the doc string. The doc string proposes the prob= argument, where it should be perc_prob=

To reproduce, ... way down at the bottom is the PI(1:10; prob=0.1) argument.

help?> PI
search: plot_density_interval PI pi Pipe pie pie! pipeline PipeBuffer sinpi cospi cispi getpid rem2pi mod2pi groupindices Pair print

  PI
  ≡≡≡≡

  Compute percentile central interval of data. Returns vector of bounds.

  PI(data; perc_prob)
  

  Required arguments
  ====================

    •  data: iterable over data values

  Optional arguments
  ====================

    •  prob::Float64=0.89: percentile interval to calculate

  Examples
  ==========

  julia> using StatisticalRethinking
  
  julia> PI(1:10)
  2-element Vector{Float64}:
   1.495
   9.505
  
  julia> PI(1:10; prob=0.1)
  2-element Vector{Float64}:
   5.05
   5.95

It got me at first.