Fix Helmholtz ID FAQ link

Thanks to the banner, I noticed the FAQ link in <login.helmholtz.de> used an older id to get to the right section of the hifis.net FAQ directly. Since it's an easy fix, I suggest to add a span with the correct id to restore the https://hifis.net/faq#helmholtz-aai link.

@jandt-desy lmkwyt ;)