[ticket/10521] Update docblock of set_cookie for new HttpOnly param

PHPBB3-10521
Merge remote-tracking branch 'github-vse/ticket/10521' into develop-ascraeus

* github-vse/ticket/10521:
  [ticket/10521] Update docblock of set_cookie for new HttpOnly param
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/10521] Update docblock of set_cookie for new HttpOnly param