Change condition for is_terminated in Zip

[haroldbruintjes]

The condition for is_terminated in the FusedStream impl for Zip should check if either child stream has terminated. Otherwise, one stream may be polled even after it has been terminated if the other has not.

This following example triggers the current bug:

use futures::stream::{self, StreamExt};

#[tokio::main]
pub async fn main() {
    let stream1 = stream::iter(vec![17, 19]);
    let stream2 = stream::iter(vec![17]);
    let mut zipped = stream1.zip(stream2);
    loop {
        futures::select!{
            res = zipped.select_next_some() => {
                println!("Zip result {res:?}");
            }
            complete => break,
        }
        
    }
}