Merge pull request #20520 from nhowell/patch-1

doc: Add missing `$`s in the Installing Rust guide

Reviewed-by: steveklabnik, steveklabnik

Author: bors

src/doc/guide.md

@@ -23,15 +23,15 @@ Linux or a Mac, all you need to do is this (note that you don't need to type
 in the `$`s, they just indicate the start of each command):
 
 ```bash
-curl -L https://static.rust-lang.org/rustup.sh | sudo sh
+$ curl -L https://static.rust-lang.org/rustup.sh | sudo sh
 ```
 
 If you're concerned about the [potential insecurity](http://curlpipesh.tumblr.com/) of using `curl | sudo sh`,
 please keep reading and see our disclaimer below. And feel free to use a two-step version of the installation and examine our installation script:
 
 ```bash
-curl -L https://static.rust-lang.org/rustup.sh -O
-sudo sh rustup.sh
+$ curl -L https://static.rust-lang.org/rustup.sh -O
+$ sudo sh rustup.sh
 ```
 
 If you're on Windows, please download either the [32-bit