docs(Navbar): remove Navbar sticky bottom (#5849)

Author: ken604

www/src/pages/components/navbar.js

@@ -151,9 +151,6 @@ export default withLayout(function NaπvbarSection({ data }) {
       <h3 className="h4">Sticky top</h3>
       <CodeBlock codeText={` <Navbar sticky="top" />`} />
 
-      <h3 className="h4">Sticky bottom</h3>
-      <CodeBlock codeText={` <Navbar sticky="bottom" />`} />
-
       <LinkedHeading h="2" id="navbars-nav-scroll">
         Scrolling
       </LinkedHeading>