[ticket/12196] Fix typo in "referrer"

Referer is a typo in the HTTP RFC and should not be used in the UI

PHPBB3-12196
Merge pull request #2665 from nickvergessen/ticket/12196-ascraeus

[ticket/12196] Fix typo in "referrer"

* nickvergessen/ticket/12196-ascraeus:
  [ticket/12196] Fix typo in "referrer"