docs: fix a couple of table of content links (testing-library#55)

Author: gnapse

README.md

@@ -88,8 +88,7 @@ when a real user uses it.
   - [TextMatch Examples](#textmatch-examples)
 - [`query` APIs](#query-apis)
 - [`queryAll` and `getAll` APIs](#queryall-and-getall-apis)
-- [`within` API](#within-api)
-- [`getQueriesForElement`](#getqueriesforelement)
+- [`within` and `getQueriesForElement` APIs](#within-and-getqueriesforelement-apis)
 - [Debugging](#debugging)
   - [`prettyDOM`](#prettydom)
 - [Implementations](#implementations)