Update firehose.mdx to explain authentication gotcha

[dom96]

As me and other developers learned recently, the authentication provided by the Bluesky firehose is limited. My preference here would be to modify the firehose to avoid sending such events in the first place, but failing that I think that it's important to at least document this.

I do still consider myself a Bluesky noob, so feedback much appreciated if I've misused any of the terminology and/or if there is a clearer way to describe these concepts.

[yamarten]

IMHO, this may rather lead to misunderstanding. Your example doesn't seem to show "authentication is limited" but "authentication does not imply data validation". The listitem does not claim to be part of another person's repository, just refer to the list there.

In addition, this is not unique to firehose, so it is difficult to find a place to write the details. I recommend that you only explain that "authenticated" here means "signed".

Alternatively, if you want to draw attention to your example, you can add it to lists tutorial.