Remove copy-paste mistake

Sorry, when changing our app name (`fern`) to `dummy-app`, I missed one.

Author: Amiel Martin

README.md

@@ -84,7 +84,7 @@ The basic index.html file built by ember-cli will look soemething like this:
     <meta name="viewport" content="width=device-width, initial-scale=1">
 
     <base href="/" />
-    <meta name="fern/config/environment" content="%7B22modulePrefix%22%3A%22dummy-app%22%7D" />
+    <meta name="dummy-app/config/environment" content="%7B22modulePrefix%22%3A%22dummy-app%22%7D" />
 
     <link rel="stylesheet" href="assets/vendor.css">
     <link rel="stylesheet" href="assets/dummy-app.css">