Reverted incorrect capitalization

doc/Ecosystem.md

@@ -29,7 +29,7 @@ We suggest a Linux or OSX development environment, though Rust related tools are
 
 The [rustup](https://www.rustup.rs/), tool manager allows you to manage multiple tool chain installations. Rust is distributed in three channels (`stable`, `beta` and `nightly`). You may set the default toolchain:
 ```
-rustup default nightly-2017-10-22-x86_64-unknown-Linux-gnu 
+rustup default nightly-2017-10-22-x86_64-unknown-linux-gnu 
 ```
 and get information on the status of `rustup`
 ```