Bug: using "not in" operator in switch works as "in" instead

Nobody has claimed this yet.

```coffee
switch
when thing in arr
console.log 'this'
when thing not in arr
console.log 'that'
```

### Expected Behavior
The above should probably compile to something along the lines of this:
```js
var indexOf = [].indexOf;

switch (false) {
case indexOf.call(arr, thing) < 0:
console.log('this');
break;
case indexOf.call(arr, thing) >= 0:
console.log('that');
}
```

### Current Behavior
It however compiles to this:
```js
var indexOf = [].indexOf;

switch (false) {
case indexOf.call(arr, thing) < 0:
console.log('this');
break;
case indexOf.call(arr, thing) < 0:
console.log('that');
}
```
### Environment

* CoffeeScript version: 2.7.0
* Node.js version: some version of 14 for legacy reasons
But the thing happens even on the "try coffeescript" page on the website too

### Other context
This does not happen in coffee v1 nor in civet with coffee compat

Reproduce the switch example with CoffeeScript 2.7.0 or on the try CoffeeScript page, then trace the compiler path that handles `in` and `not in` conditions in switch cases. Done means the generated cases use opposite comparisons so the membership and non-membership branches behave as expected.

Written by the indexing model from the issue text.