If duplicate notes are already in the collection and, based on the first
field of all of them, they should be updated, update all of them instead
of just the first one we come across.
When "allow HTML" was turned off, Anki was replacing newlines with <br>s
in the text of the new notes before it escaped HTML characters, so the
line breaks were becoming <br>.
Even if there are several (duplicate) notes in the collection that
match, only send the message once to avoid making it look like multiple
dupes have been added.
