demo(accordion): fix typo in demo's readme

src/accordion/docs/readme.md

@@ -1,4 +1,4 @@
-sThe **accordion directive** builds on top of the collapse directive to provide a list of items, with collapsible bodies that are collapsed or expanded by clicking on the item's header.
+The **accordion directive** builds on top of the collapse directive to provide a list of items, with collapsible bodies that are collapsed or expanded by clicking on the item's header.
 
 We can control whether expanding an item will cause the other items to close, using the `close-others` attribute on accordion.