Shorten paragraph about builtin server

docs/deploying/index.rst

@@ -3,13 +3,10 @@
 Deployment Options
 ==================
 
-Flask's builtin server is lightweight and easy to use, but it has multiple
-problems which you don't want to face in production. With default settings, it
-can handle only one request at a time, and even if you manage to circumvent
-this problem, it has too many scaling problems that would make it unsuitable
-for production. **Do not use the builtin development server in production**.
-Some of the options available for properly running Flask in production are
-documented here.
+While lightweight and easy to use, **Flask's built-in server is not suitable
+for production** as it doesn't scale well and by default serves only one
+request at a time.  Some of the options available for properly running Flask in
+production are documented here.
 
 If you want to deploy your Flask application to a WSGI server not listed here,
 look up the server documentation about how to use a WSGI app with it.  Just