Drop $1 recognizer

[nightkr]

It's not very good, and it has mislead several people into thinking that it's a premium feature that needs to be unlocked somehow.

Let's kill it, but keep the infra for alternative recognizers around.

• [x] Fix enum setting infra so that invalid (removed) options are ignored instead of crashing the app
• [x] Remove the option
• [x] Hide enum settings with only one option (so that it can be reintroduced later, if needed)