A typo in form login doc

[binkoni]

Describe the bug
There is a typo in form login section on the doc

A link to the Authentication class is written as ref:servlet/authentication/architecture.adoc#servlet-authentication-authentication[Authentication]

To Reproduce
Visit form login

Expected behavior
It should be written like:

xref:servlet/authentication/architecture.adoc#servlet-authentication-authentication[Authentication]