Fix links in blog

Author: alexcrichton

_posts/2018-01-04-Rust-1.23.md

@@ -50,7 +50,7 @@ they've found.
 [since October of last year]: https://github.com/rust-lang/rust/pull/45324
 
 In other documentation news, historically, Cargo's docs have been a bit strange.
-Rather than being on [https://doc.rust-lang.org][], they've been at [https://doc.crates.io][].
+Rather than being on https://doc.rust-lang.org, they've been at https://doc.crates.io.
 With this release, [that's changing](https://github.com/rust-lang/rust/pull/45692).
 You can now find Cargo's docs at [https://doc.rust-lang.org/cargo][]. Additionally, they've
 been converted to the same format as our other long-form documentation. We'll be