MAINT: avoid spurious warnings in binom(n, p=0).mean() etc

closes gh-3817
DOC: typo
Merge pull request #3850 from argriffing/eig-docstring-typo

DOC: typo in linalg.eig docstring
Merge pull request #3820 from ev-br/binom_warn

MAINT: avoid spurious warnings in binom(n, p=0).mean() etc