Fixed a small typo

app/assets/stylesheets/grid/_outer-container.scss

@@ -1,6 +1,6 @@
 @charset "UTF-8";
 
-/// Makes an element a outer container by centring it in the viewport, clearing its floats, and setting its `max-width`.
+/// Makes an element a outer container by centering it in the viewport, clearing its floats, and setting its `max-width`.
 /// Although optional, using `outer-container` is recommended. The mixin can be called on more than one element per page, as long as they are not nested.
 ///
 /// @param {Number [unit]} $local-max-width [$max-width]