Fixed broken link

The "searching" link was 404ing

readme.md

@@ -191,7 +191,7 @@ Because we can't (easily) use ElasticSearch for this demo, we use wagtail's nati
 However, native DB search can't search specific fields in our models on a generalized `Page` query.
 So for demo purposes ONLY, we hard-code the model names we want to search into `search.views`, which is
 not ideal. In production, use ElasticSearch and a simplified search query, per
-[http://docs.wagtail.io/en/v1.8.1/topics/search/searching.html](http://docs.wagtail.io/en/v1.8.1/topics/search/searching.html).
+[http://docs.wagtail.io/en/v1.13.1/topics/search/searching.html](http://docs.wagtail.io/en/v1.13.1/topics/search/searching.html).
 
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