doc: sync interval.rs and time/mod.rs docs
//!
//! A simple example using [`interval`] to execute a task every two seconds.
//!
-//! The difference between [`interval`] and [`sleep`] is that an
-//! [`interval`] measures the time since the last tick, which means that
-//! `.tick().await` may wait for a shorter time than the duration specified
-//! for the interval if some time has passed between calls to `.tick().await`.
+//! The difference between [`interval`] and [`sleep`] is that an [`interval`]
+//! measures the time since the last tick, which means that `.tick().await`
+//! may wait for a shorter time than the duration specified for the interval
+//! if some time has passed between calls to `.tick().await`.
//!
//! If the tick in the example below was replaced with [`sleep`], the task
//! would only be executed once every three seconds, and not every two
//!
//! #[tokio::main]
//! async fn main() {
-//! let interval = time::interval(time::Duration::from_secs(2));
-//! tokio::pin!(interval);
-//!
+//! let mut interval = time::interval(time::Duration::from_secs(2));
//! for _i in 0..5 {
-//! interval.as_mut().tick().await;
+//! interval.tick().await;
//! task_that_takes_a_second().await;
//! }
//! }
