Broken link in the servlet starting page adoc

[Ruffeng]

Describe the bug
There's one of the links on the home page that does not lead you to the desired section. This is because the headline has a different ID than the anchor name. Checking the adocs page, it seems that the headline has 2 specific id and it only processes the last one(which doesn't match)

To Reproduce
Steps to reproduce the behaviour. go into the page and search for "Better understand what Spring Boot enables in Spring Security by default". You will notice that this link goes nowhere when clicked.

Expected behaviour
I expect to go into the next section called Runtime Expectations

[Ruffeng]

I created a PR for it #14119, which contains the adaption to the newest identifier added to the page. This should fix the link

[marcusdacoregio]

Thanks @Ruffeng, closing in favor of #14119 .