docs(readme): Fix Yarn website link (#219)

francoischalifour · web-flow · commit 700e44e2b464 · 2018-09-03T13:04:06.000+02:00
diff --git a/README.md b/README.md
@@ -43,7 +43,7 @@ npm start
 
 ---
 
-Alternatively, you can use [Yarn](https://http://yarnpkg.com):
+Alternatively, you can use [Yarn](https://yarnpkg.com):
 
 ```
 yarn create instantsearch-app my-app
