Strip backslashes

Removed the trailing backslash of the last non-empty line.

This changes:

```
http GET "http://httpbin.org/get?param1=value1&param2=value2" \
    "X-Special-Header:7gi2SLiwruFl80QigSjulHrHtVk3iDto" \
    "Content-Type:application/json" \
```

 to

```
http GET "http://httpbin.org/get?param1=value1&param2=value2" \
    "X-Special-Header:7gi2SLiwruFl80QigSjulHrHtVk3iDto" \
    "Content-Type:application/json"
```