fix(docs-infra): remove scrollbar styles for accessibility (#38852)

This commit removes the scrollbar styles so that the default
styles in the browser render. This widens the webkit scroll bar.
This makes it easier to grab the scrollbar using assistive
technology and devices, and provides a wider target for
those who have dexterity issues. By removing these styles,
We will no longer have to maintain custom scrollbars specific to WebKit
and they will be accessible by default.

PR Close #38852

aio/src/styles/2-modules/_modules-dir.scss

@@ -25,7 +25,6 @@
    @import 'progress-bar';
    @import 'presskit';
    @import 'resources';
-   @import 'scrollbar';
    @import 'search-results';
    @import 'select-menu';
    @import 'table';

aio/src/styles/2-modules/_scrollbar.scss

@@ -1,27 +0,0 @@
-body::-webkit-scrollbar, mat-sidenav.sidenav::-webkit-scrollbar, .mat-sidenav-content::-webkit-scrollbar {
-  height: 6px;
-  width: 6px;
-}
-
-body::-webkit-scrollbar-track, mat-sidenav.sidenav::-webkit-scrollbar-track, .mat-sidenav-content::-webkit-scrollbar-track {
-  -webkit-box-shadow: inset 0 0 6px rgba(0,0,0,0.3);
-}
-
-body::-webkit-scrollbar-thumb, mat-sidenav.sidenav::-webkit-scrollbar-thumb, .mat-sidenav-content::-webkit-scrollbar-thumb {
-  background-color: $mediumgray;
-  outline: 1px solid $darkgray;
-}
-
-.search-results::-webkit-scrollbar, .toc-container::-webkit-scrollbar {
-  height: 4px;
-  width: 4px;
-}
-
-.search-results::-webkit-scrollbar-track, .toc-container::-webkit-scrollbar-track {
-  -webkit-box-shadow: inset 0 0 6px rgba(0,0,0,0.3);
-}
-
-.search-results::-webkit-scrollbar-thumb, .toc-container::-webkit-scrollbar-thumb {
-  background-color: $mediumgray;
-  outline: 1px solid slategrey;
-}