[MA-33]: Added aria-live to empty result messages (#29814)

Co-authored-by: Mattermost Build <build@mattermost.com>

webapp/channels/src/components/search_results/search_results.tsx

@@ -292,6 +292,7 @@ const SearchResults: React.FC<Props> = (props: Props): JSX.Element => {
                     'sidebar--right__subheader a11y__section',
                     {'sidebar-expanded': isSideBarExpanded},
                 ])}
+                aria-live='polite'
             >
                 <NoResultsIndicator
                     style={{padding: '48px'}}
@@ -307,6 +308,7 @@ const SearchResults: React.FC<Props> = (props: Props): JSX.Element => {
                     'sidebar--right__subheader a11y__section',
                     {'sidebar-expanded': isSideBarExpanded},
                 ])}
+                aria-live='polite'
             >
                 <NoResultsIndicator
                     style={{padding: '48px'}}
@@ -408,7 +410,6 @@ const SearchResults: React.FC<Props> = (props: Props): JSX.Element => {
             >
                 <div
                     id='search-items-container'
-                    role='application'
                     className={classNames([
                         'search-items-container post-list__table a11y__region',
                         {