[Cookbook][Configuration] tweaks for the web server configuration chapter

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | yes
| Applies to    | all
| Fixed tickets | 

Tweaks to #3915 as suggested by @weaverryan.
I wonder if it is a good idea to merge #4000 first, to be able to link "PHP's internal web server" directly to that article.