fix docustring on fetch_or

Author: agavra

library/core/src/sync/atomic.rs

@@ -1151,8 +1151,8 @@ impl AtomicBool {
     /// assert_eq!(foo.fetch_or(false, Ordering::SeqCst), true);
     /// assert_eq!(foo.load(Ordering::SeqCst), true);
     ///
-    /// let foo = AtomicBool::new(true);
-    /// assert_eq!(foo.fetch_or(true, Ordering::SeqCst), true);
+    /// let foo = AtomicBool::new(false);
+    /// assert_eq!(foo.fetch_or(true, Ordering::SeqCst), false);
     /// assert_eq!(foo.load(Ordering::SeqCst), true);
     ///
     /// let foo = AtomicBool::new(false);