fix comment: not fourth but sixth argument
minor #11811 [HttpFoundation] fix comment: not fourth but sixth argument (DQNEO)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #11811).

Discussion
----------

[HttpFoundation] fix comment: not fourth but sixth argument

$server is the **sixth** argument, not fourth.

| Q             | A
| ------------- | ---
| Bug fix?      | no,
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

Commits
-------

42841e8 fix comment: not fourth but sixth argument