DOC: Simplifies Mandelbrot set plot in Quickstart guide (#18712)
DOC: Simplifies Mandelbrot set plot in Quickstart guide (#18712)

Closes gh-18409
jakirkham/numpy,pdebuyl/numpy,numpy/numpy,rgommers/numpy,endolith/numpy,mhvk/numpy,mhvk/numpy,endolith/numpy,simongibbons/numpy,pbrod/numpy,rgommers/numpy,mattip/numpy,mhvk/numpy,jakirkham/numpy,pbrod/numpy,numpy/numpy,seberg/numpy,endolith/numpy,simongibbons/numpy,pdebuyl/numpy,simongibbons/numpy,jakirkham/numpy,rgommers/numpy,endolith/numpy,charris/numpy,simongibbons/numpy,anntzer/numpy,pdebuyl/numpy,pbrod/numpy,mattip/numpy,anntzer/numpy,mhvk/numpy,pbrod/numpy,simongibbons/numpy,jakirkham/numpy,charris/numpy,numpy/numpy,anntzer/numpy,mattip/numpy,seberg/numpy,rgommers/numpy,charris/numpy,charris/numpy,numpy/numpy,anntzer/numpy,seberg/numpy,mattip/numpy,jakirkham/numpy,mhvk/numpy,pbrod/numpy,pdebuyl/numpy,seberg/numpy