fixes typo in equation for Poisson cumulative distribution function (#15138)
fixes typo in equation for Poisson cumulative distribution function (#15138)


scipy/scipy,anntzer/scipy,scipy/scipy,scipy/scipy,zerothi/scipy,scipy/scipy,Stefan-Endres/scipy,Stefan-Endres/scipy,andyfaff/scipy,endolith/scipy,endolith/scipy,tylerjereddy/scipy,rgommers/scipy,ilayn/scipy,zerothi/scipy,endolith/scipy,anntzer/scipy,tylerjereddy/scipy,ilayn/scipy,perimosocordiae/scipy,anntzer/scipy,rgommers/scipy,mdhaber/scipy,tylerjereddy/scipy,scipy/scipy,rgommers/scipy,WarrenWeckesser/scipy,mdhaber/scipy,anntzer/scipy,andyfaff/scipy,perimosocordiae/scipy,zerothi/scipy,rgommers/scipy,perimosocordiae/scipy,endolith/scipy,vigna/scipy,andyfaff/scipy,endolith/scipy,vigna/scipy,scipy/scipy,vigna/scipy,ilayn/scipy,andyfaff/scipy,zerothi/scipy,WarrenWeckesser/scipy,WarrenWeckesser/scipy,anntzer/scipy,mdhaber/scipy,ilayn/scipy,Stefan-Endres/scipy,Stefan-Endres/scipy,perimosocordiae/scipy,mdhaber/scipy,vigna/scipy,andyfaff/scipy,WarrenWeckesser/scipy,zerothi/scipy,mdhaber/scipy,WarrenWeckesser/scipy,ilayn/scipy,Stefan-Endres/scipy,perimosocordiae/scipy,andyfaff/scipy,ilayn/scipy,mdhaber/scipy,perimosocordiae/scipy,Stefan-Endres/scipy,WarrenWeckesser/scipy,endolith/scipy,vigna/scipy,anntzer/scipy,tylerjereddy/scipy,rgommers/scipy,zerothi/scipy,tylerjereddy/scipy