Update index.mdx (#2865)

Removes double "already" in sentence.

website/docs/tutorial/index.mdx

@@ -29,7 +29,7 @@ the free [Rust Book](https://doc.rust-lang.org/book/ch00-00-introduction.html) o
 beginners and continues to be an excellent resource even for experienced Rust developers.
 
 Ensure the latest version of Rust is installed by running `rustup update` or by
-[installing rust](https://www.rust-lang.org/tools/install) if you haven't already done so already.
+[installing rust](https://www.rust-lang.org/tools/install) if you haven't already done so.
 
 After installing Rust, you can use Cargo to install `trunk` by running: