remove throttle example

Signed-off-by: Yoshua Wuyts <yoshuawuyts@gmail.com>

examples/throttle.rs

@@ -1,27 +0,0 @@
-//! Spawns a timed task which gets throttled.
-
-fn main() {
-    #[cfg(feature = "unstable")]
-    {
-        use async_std::prelude::*;
-        use async_std::task;
-
-        task::block_on(async {
-            use async_std::stream;
-            use std::time::Duration;
-
-            // emit value every 1 second
-            let s = stream::interval(Duration::from_secs(1)).enumerate();
-
-            // throttle for 2 seconds
-            let s = s.throttle(Duration::from_secs(2));
-
-            s.for_each(|(n, _)| {
-                dbg!(n);
-            })
-            .await;
-            // => 0 .. 1 .. 2 .. 3
-            // with a pause of 2 seconds between each print
-        })
-    }
-}