docs: Update devlogin screenshot and url in development setup.

This commit replaces the old dev login screenshot with the new one.
This also replaces the default path that we mention in the docs to
localhost:9991/devlogin.

docs/development/remote.md

@@ -81,10 +81,10 @@ you cloned Zulip:
 ```
 
 This will start up the Zulip server on port 9991. You can then
-navigate to `http://<REMOTE_IP>:9991` and you should see something like
+navigate to `http://<REMOTE_IP>:9991/devlogin` and you should see something like
 this screenshot of the Zulip development environment:
 
-![Image of Zulip development environment](../images/zulip-dev.png)
+![Image of Zulip development environment](../images/zulip-devlogin.png)
 
 The `--interface=''` option makes the Zulip development environment
 accessible from any IP address (in contrast with the much more secure

docs/development/setup-recommended.md

@@ -404,11 +404,11 @@ webpack: bundle is now VALID.
 ```
 
 Now the Zulip server should be running and accessible. Verify this by
-navigating to <http://localhost:9991/> in the browser on your main machine.
+navigating to <http://localhost:9991/devlogin> in the browser on your main machine.
 
 You should see something like this:
 
-![Image of Zulip development environment](../images/zulip-dev.png)
+![Image of Zulip devlogin](../images/zulip-devlogin.png)
 
 The Zulip server will continue to run and send output to the terminal window.
 When you navigate to Zulip in your browser, check your terminal and you