Fix tc358743 identifier in the /boot/config.txt population

[mtlynch]

This fixes a small bug in the tinypilot.postinst that was preventing it from matching the right line in /boot/config.txt to add the dtoverlay=tc358743-audio line.

Peer testing

To test this bundle run:

curl \
  --silent \
  --show-error \
  --location \
  https://raw.githubusercontent.com/tiny-pilot/tinypilot/master/scripts/install-bundle | \
  sudo bash -s -- \
    https://output.circle-artifacts.com/output/job/0bcd7da3-9a88-4126-ada8-6a7804e02dfe/artifacts/0/bundler/dist/tinypilot-community-20230901T1500Z-1.9.0-75+03827f4.tgz && \
  sudo reboot

[mtlynch]

Automated comment from CodeApprove ➜

⏳ @db39 please review this Pull Request

[mtlynch]

@db39 - Can you try the peer test on a bare Raspbian system with TC358743 enabled and make sure you hear audio? I'm getting inconsistent results with audio, but I still see the issue on 2.6.0, so I can't figure out if there's something off in my environment, or if there's something we've introduced in 2.6.1.

[mtlynch]

@db39 - Sorry to rush, but this one is a high priority, as I'm aiming to cut a release candidate by EOD.

[db39]

@mtlynch - No worries - starting testing now.

[db39]

Audio worked fine in my testing (bare Raspian Bullseye 32-bit).

[mtlynch]

Great, thanks!