[Backport staging] Fix rightpanel hiding scrollbar (#11832)

Co-authored-by: Kerry <kerrya@element.io>

res/css/views/right_panel/_BaseCard.pcss

@@ -88,9 +88,6 @@ limitations under the License.
     }
 
     .mx_AutoHideScrollbar {
-        /* collapse the margin into a padding to move the scrollbar into the right gutter */
-        margin-right: -8px;
-        padding-right: 8px;
         min-height: 0;
         width: 100%;
         height: 100%;