right sidebar: Move right sidebar to the right.

Move the right sidebar which is a bit to the left, to the
right side of the page. The entire column is moved to the right.
The change is brought about by removing "right" CSS property on
'column-right' class
Fixes zulip#17307

static/js/scroll_bar.js

@@ -46,7 +46,6 @@ export function initialize() {
         $(".fixed-app").css("left", "-" + sbWidth + "px");
         $(".fixed-app .column-middle").css("margin-left", 7 + sbWidth + "px");
 
-        $(".column-right").css("right", sbWidth + "px");
         $(".app-main .right-sidebar").css({
             "margin-left": sbWidth + "px",
             width: 250 - sbWidth + "px",