fix grammar

Author: steveklabnik

_posts/2017-11-22-Rust-1.22.md

@@ -8,7 +8,7 @@ The Rust team is happy to announce *two* new versions of Rust, 1.22.0 and
 1.22.1. Rust is a systems programming language focused on safety, speed, and
 concurrency.
 
-> Wait, two versions? At the last moment, we [discovered a a late-breaking
+> Wait, two versions? At the last moment, we [discovered a late-breaking
 > issue with the new macOS High
 > Sierra](https://github.com/rust-lang/rust/pull/46183) in 1.22.0, and for
 > various reasons, decided to release 1.22.0 as usual, but also put out a