RequireCodeOwnerReviews cannot be set to false when updating

[leopoldwang]

RequireCodeOwnerReviews field does not use pointer type causing json encode to omit the field. Request was then rejected by github rest api

go-github/github/repos.go

Line 948 in 2be8000

RequireCodeOwnerReviews bool `json:"require_code_owner_reviews,omitempty"`

[gmlewis]

Thank you, @leopoldwang !
Would you like to create a PR to fix this issue, or shall I open this up to anyone to create a PR?