Example syntax for capture inlay hints setting is outdated

Captures example in Effekt VSCode settings uses the following outdated syntax:

The current syntax is (where `'` is used to indicate the inlay hint part, the real syntax is unquoted - better ideas welcome):

```
def main() 'at {io}': Unit = println("Hello Effekt!")
```

The following part of `package.json` needs to be adjusted: https://github.com/effekt-lang/effekt-vscode/blob/master/package.json#L153