Adjust documentation

Author: Nelspike

README.md

@@ -469,7 +469,7 @@ fastify.get('/responseDescription', {
 }, () => {})
 ```
 
-Additionally, if you provide a `$ref` in your response schema but no description, if your `$ref` base schema includes a description, that will be used.
+Additionally, if you provide a `$ref` in your response schema but no description, the reference's description will be used as a fallback.
 
 <a name="route.response.2xx"></a>
 ##### Status code 2xx