Rollup merge of rust-lang#60489 - GuillaumeGomez:remove-hamburger, r=QuietMisdreavus

Remove hamburger button from source code page

Fixes rust-lang#60483.

Screenshot:

<img width="575" alt="Screenshot 2019-05-03 at 00 12 51" src="https://user-images.githubusercontent.com/3050060/57110298-61ec8f00-6d38-11e9-85fd-d13be94b9c52.png">

cc @rust-lang/rustdoc

Author: Centril

src/librustdoc/html/static/rustdoc.css

@@ -1052,6 +1052,10 @@ h3 > .collapse-toggle, h4 > .collapse-toggle {
 		height: 45px;
 	}
 
+	.rustdoc.source > .sidebar > .sidebar-menu {
+		display: none;
+	}
+
 	.sidebar-elems {
 		position: fixed;
 		z-index: 1;