Add disabled style to symbol palette tabs (#19171)

GitOrigin-RevId: 9fbb92bbc08cd7b9a00b00c46974b93d19360a4a

services/web/frontend/stylesheets/modules/symbol-palette.less

@@ -56,6 +56,11 @@
       background: @symbol-palette-selected-tab-bg;
       color: @symbol-palette-selected-tab-color;
     }
+
+    &:disabled {
+      cursor: default;
+      opacity: 0.25;
+    }
   }
 
   .symbol-palette-body {