Update Verify docs for new warning #162
Description
Verify now gives this message (in orange) for claims signed by a cert not on trust list:
The Content Credential issuer couldn’t be recognized. This file may not come from where it claims to.
Update docs to reflect this vs. old warning.
Cf https://discord.com/channels/983153151341371422/1276934105858314404/1280590516001701920