[lib] Fix selecting custom Neynar channel

Summary:
This addresses ENG-9340.

We were comparing the human-readable name when we should be comparing the channel ID.

Test Plan:

1. I compiled a prod build to a local iOS simulator
2. I logged in as a prod user with a linked Farcaster account
3. I went to the three-dots settings menu for a community that the user is an admin of, and selected "Tag Farcaster channel"
4. I selected the "other" option and then typed in "new-york"
5. I confirmed I was able to link the channel successfully

Reviewers: will, varun

Reviewed By: will

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D13717