Fix a typo re: on_response -> on_complete

docs/middleware/custom.md

@@ -48,10 +48,12 @@ later, response. Some keys are:
 There's an easier way to write middleware, and it's also the recommended one: make your middleware subclass `Faraday::Middleware`.
 `Faraday::Middleware` already implements the `#call` method for you and looks for two methods in your subclass: `#on_request(env)` and `#on_complete(env)`.
 `#on_request` is called when the request is being built and is given the `env` representing the request.
+
 `#on_complete` is called after the response has been received (that's right, it already supports parallel mode!) and receives the `env` of the response.
 
 ### Do I need to override `#call`?
 
-For the majority of middleware, it's not necessary to override the `#call` method, as you can simply use `#on_request` and `#on_response`.
+For the majority of middleware, it's not necessary to override the `#call` method. You can instead use `#on_request` and `#on_complete`.
+
 However, in some cases you may need to wrap the call in a block, or work around it somehow (think of a begin-rescue, for example).
-When that happens, then you can simply override `#call`. When you do so, remember to call either `app.call(env)` or `super` to avoid breaking the middleware stack call!
+When that happens, then you can override `#call`. When you do so, remember to call either `app.call(env)` or `super` to avoid breaking the middleware stack call!