Remove CSS declarations which change default scrollbar width

Setting the declaration "scrollbar-width: thin" has a legitimate accessibility concern, though doing so could have made sense previously for some reason. Let's prefer each OS and its desktop environments' setting over Element's aesthetic view.

See: https://developer.mozilla.org/en-US/docs/Web/CSS/scrollbar-width#accessibility

Signed-off-by: Suguru Hirahara <luixxiul@users.noreply.github.com>

res/css/structures/_AutoHideScrollbar.pcss

@@ -1,24 +1,15 @@
 /*
 Copyright 2018-2024 New Vector Ltd.
+Copyright 2024 Suguru Hirahara
 
 SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only
 Please see LICENSE files in the repository root for full details.
 */
 
-/* make any scrollbar grey and thin */
+/* make any scrollbar grey */
 html {
     scrollbar-color: $scrollbar-thumb-color transparent;
 }
-/* scrollbar-width is not inherited (but -color is, why?!), */
-/* so declare it on every element */
-* {
-    scrollbar-width: thin;
-}
-
-::-webkit-scrollbar {
-    width: 6px;
-    height: 6px;
-}
 
 ::-webkit-scrollbar-thumb {
     border-radius: 3px;