Fixed description of session storage of the ApiKeyAuthenticator

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.4
| Fixed tickets | #4060

I assume the authentication is needed for each request (even if token is stored in the session)
since you can add custom logic in the authenticator.
To pick up your previous argument, docs should be simple. I wanted to highlight the
small code addition without changing the entire structure. And I find it personally also
easier to read through code if I am able to avoid nested divs.