Non-blocking typo fix (#34935)

site/content/docs/5.1/customize/optimize.md

@@ -71,7 +71,7 @@ Lastly, this [CSS Tricks article on unused CSS](https://css-tricks.com/how-do-yo
 
 Whenever possible, be sure to compress all the code you serve to your visitors. If you're using Bootstrap dist files, try to stick to the minified versions (indicated by the `.min.css` and `.min.js` extensions). If you're building Bootstrap from the source with your own build system, be sure to implement your own minifiers for HTML, CSS, and JS.
 
-## Nonblocking files
+## Non-blocking files
 
 While minifying and using compression might seem like enough, making your files nonblocking ones is also a big step in making your site well-optimized and fast enough.