Fix documentation in Cell

library/core/src/cell.rs

@@ -349,7 +349,7 @@ pub fn set(&self, val: T) {
         drop(old);
     }
 
-    /// Swaps the values of two Cells.
+    /// Swaps the values of two `Cell`s.
     /// Difference with `std::mem::swap` is that this function doesn't require `&mut` reference.
     ///
     /// # Examples