[Rd] intersect() change of behavior in 4.2

[Gábor Csárdi]

I wonder if this change is intentional, and if it is, whether it is
worth mentioning in the NEWS.

❯ R-4.1 -q -e 'intersect(list(), "foo")'
> intersect(list(), "foo")
character(0)

❯ R-4.2 -q -e 'intersect(list(), "foo")'
> intersect(list(), "foo")
list()