Replace DurationExceedsTimestamp example with a note.

src/round.rs

@@ -235,15 +235,7 @@ where
 pub enum RoundingError {
     /// Error when the Duration exceeds the Duration from or until the Unix epoch.
     ///
-    /// ``` rust
-    /// # use chrono::{DurationRound, Duration, RoundingError, TimeZone, Utc};
-    /// let dt = Utc.with_ymd_and_hms(1970, 12, 12, 0, 0, 0).unwrap();
-    ///
-    /// assert_eq!(
-    ///     dt.duration_round(Duration::days(365)),
-    ///     Err(RoundingError::DurationExceedsTimestamp),
-    /// );
-    /// ```
+    /// Note: this error is not produced anymore.
     DurationExceedsTimestamp,
 
     /// Error when `Duration.num_nanoseconds` exceeds the limit.