Unable to disable bridges after they have been configured and successfully bootstrapped

Reported in #tor-browser-dev and I've successfully repro'd on 13.5a8.

It seems toggling off Use a bridge doesn't get applied in the backend, though the UI works. Restarting the browser and going back to the relevant UI shows the toggle back on. However, this toggling does persist if you have not bootstrapped. IE:

• Launch TBA first time
• Toggle use bridge on, then off
• Relaucnh
• Use a bridge is still off

So it seems bootstrapping is somehow gating settings being applied?

/cc @qbi