scroll_bar: Remove unnessary adjustment of keyboard icon.

Since the keyboard icon is not associated with scrollbar, we
can just have a fixed margin-right for it.

static/js/scroll_bar.js

@@ -48,7 +48,6 @@ export function initialize() {
 
         // Align floating recipient bar with the middle column.
         $(".fixed-app").css("left", "-" + sbWidth / 2 + "px");
-        $("#keyboard-icon").css({"margin-right": sbWidth + "px"});
     }
     set_layout_width();
 }

static/styles/right_sidebar.css

@@ -208,6 +208,7 @@
     position: relative;
     cursor: pointer;
     font-size: 20px;
+    margin-right: 15px;
 }
 
 #sidebar-keyboard-shortcuts {