Update atlas-higgs-challenge-2014.xml

Fixing the typos mentioned in the mail.
- citation recommendation needs to be adjusted by @pamfilos as he creates them automatically
- is the \<p\> showing due to the format as the record doesn't have authors?
This duplicates K.B. which was already the first author.  I guess you wanted to enrich authors of record 331; I'll move them there and change the order as per @dhrou's email.