[lang] Update Goodreads API key instructions (#6542)

Closes <https://github.com/koreader/koreader/issues/6539>.

plugins/goodreads.koplugin/main.lua

@@ -87,9 +87,8 @@ function Goodreads:updateSettings()
 How to generate a key and a secret key:
 
 1. Go to https://www.goodreads.com/user/sign_up and create an account
-2. Register for a development key on the following page: https://www.goodreads.com/user/sign_in?rd=true
+2. Create a key and secret key on https://www.goodreads.com/api/keys
-3. Your key and secret key will now be available on https://www.goodreads.com/api/key
+3. Enter your generated key and your secret key in the settings dialog (Login to Goodreads window)
-4. Enter your generated key and your secret key in the settings dialog (Login to Goodreads window)
 ]])
 
     if self.goodreads_key == "" then