remove unnecessary docs sections for media queries page

docs/_data/nav.yml

@@ -17,9 +17,6 @@
   pages:
     - title: Scaffolding
     - title: Media queries
-      sections:
-        - title: Common queries
-        - title: Sass mixins
     - title: Containers
     - title: Grid
       sections:

docs/layout/media-queries.md

@@ -5,8 +5,6 @@ title: Media queries
 
 Since Bootstrap is designed to be mobile-first, we employ media queries in our CSS to create responsive pages and components. Media queries allow you to group rulesets by a handful of parameters, most notably viewport dimensions, to gracefully scale content across devices.
 
-### Common queries
-
 Bootstrap mainly uses the following media query ranges in our source Sass files for key breakpoints in our layout, grid system, and components.
 
 {% highlight scss %}