req.path is incorrect when path ends with slash

req.path is set like below.

```
1. https://domain/test => req.path = '/test'
2. https://domain/test/ => req.path = '/test'
```

2 is not correct, since Express actually set '/test/' to path in this case.

I think the cause is that the `req.path` is obtained from `event.pathparameters.proxy` instead of `event.path`, and the last slash is not included in `event.pathparameters.proxy`.