fix: remove incorrect visibility for sub-menu indicator (#10506)

Author: web-padawan

packages/context-menu/src/styles/vaadin-context-menu-item-base-styles.js

@@ -15,7 +15,6 @@ const menuItemStyles = css`
     height: var(--vaadin-icon-size, 1lh);
     mask: var(--_vaadin-icon-chevron-down) 50% / var(--vaadin-icon-visual-size, 100%) no-repeat;
     rotate: -90deg;
-    visibility: hidden;
     width: var(--vaadin-icon-size, 1lh);
   }
 

packages/menu-bar/test/visual/base/menu-bar.test.js

@@ -29,7 +29,13 @@ describe('menu-bar', () => {
             { text: 'Home' },
             {
               text: 'Reports',
-              children: [{ text: 'View Reports' }, { text: 'Generate Report' }],
+              children: [
+                { text: 'View Reports' },
+                {
+                  text: 'Generate Report',
+                  children: [{ text: 'Monthly' }, { text: 'Yearly' }],
+                },
+              ],
             },
             { text: 'Dashboard', disabled: true },
             { text: 'Help' },