[MA-23]: Updated the aria-label property of sidebar expand button (#29660)

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

webapp/channels/src/components/post_edit_history/__snapshots__/post_edit_history.test.tsx.snap

@@ -30,15 +30,16 @@ exports[`components/post_edit_history should display error screen if errors are
             class="pull-right"
           >
             <button
+              aria-label="Expand Sidebar Icon"
               class="sidebar--right__expand btn btn-icon btn-sm"
               type="button"
             >
               <i
-                aria-label="Expand Sidebar Icon"
+                aria-hidden="true"
                 class="icon icon-arrow-expand"
               />
               <i
-                aria-label="Collapse Sidebar Icon"
+                aria-hidden="true"
                 class="icon icon-arrow-collapse"
               />
             </button>
@@ -192,15 +193,16 @@ exports[`components/post_edit_history should match snapshot 1`] = `
             class="pull-right"
           >
             <button
+              aria-label="Expand Sidebar Icon"
               class="sidebar--right__expand btn btn-icon btn-sm"
               type="button"
             >
               <i
-                aria-label="Expand Sidebar Icon"
+                aria-hidden="true"
                 class="icon icon-arrow-expand"
               />
               <i
-                aria-label="Collapse Sidebar Icon"
+                aria-hidden="true"
                 class="icon icon-arrow-collapse"
               />
             </button>

webapp/channels/src/components/search_results_header/search_results_header.tsx

@@ -48,6 +48,8 @@ function SearchResultsHeader(props: Props) {
         </>
     );
 
+    const expandOrCollapseSidebarButtonAriaLabel = props.isExpanded ? formatMessage({id: 'rhs_header.collapseSidebarTooltip.icon', defaultMessage: 'Collapse Sidebar Icon'}) : formatMessage({id: 'rhs_header.expandSidebarTooltip.icon', defaultMessage: 'Expand Sidebar Icon'});
+
     return (
         <div className='sidebar--right__header'>
             <span className='sidebar--right__title'>
@@ -71,14 +73,15 @@ function SearchResultsHeader(props: Props) {
                             type='button'
                             className='sidebar--right__expand btn btn-icon btn-sm'
                             onClick={props.actions.toggleRhsExpanded}
+                            aria-label={expandOrCollapseSidebarButtonAriaLabel}
                         >
                             <i
                                 className='icon icon-arrow-expand'
-                                aria-label={formatMessage({id: 'rhs_header.expandSidebarTooltip.icon', defaultMessage: 'Expand Sidebar Icon'})}
+                                aria-hidden='true'
                             />
                             <i
                                 className='icon icon-arrow-collapse'
-                                aria-label={formatMessage({id: 'rhs_header.collapseSidebarTooltip.icon', defaultMessage: 'Collapse Sidebar Icon'})}
+                                aria-hidden='true'
                             />
                         </button>
                     </WithTooltip>