RELEASES.md: ? is one of three Kleene operators
RELEASES.md: ? is one of three Kleene operators

The slash and quotes in ?/“Kleene” appeared to define “Kleene” as the
name for the ? operator, which is not the case.  Rust has three Kleene
operators *, +, ?.

(Pointed out by /u/Sharlinator on Reddit.)

Signed-off-by: Anders Kaseorg <087231934ba8fcf78bc142ce37d193b895ac03c4@mit.edu>

graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust