Apply suggestions from code review

Co-authored-by: Trevor Gross <t.gross35@gmail.com>

Author: tisonkun

library/core/src/cell/once.rs

@@ -184,11 +184,13 @@ impl<T> OnceCell<T> {
     ///
     /// let mut cell = OnceCell::new();
     /// let value = cell.get_mut_or_init(|| 92);
-    /// assert_eq!(value, &92);
+    /// assert_eq!(*value, 92);
+    ///
     /// *value += 2;
-    /// assert_eq!(value, &94);
+    /// assert_eq!(*value, 94);
+    ///
     /// let value = cell.get_mut_or_init(|| unreachable!());
-    /// assert_eq!(value, &94);
+    /// assert_eq!(*value, 94);
     /// ```
     #[inline]
     #[unstable(feature = "once_cell_get_mut", issue = "121641")]
@@ -259,15 +261,16 @@ impl<T> OnceCell<T> {
     ///
     /// use std::cell::OnceCell;
     ///
-    /// let mut cell = OnceCell::new();
-    /// assert_eq!(cell.get_mut_or_try_init(|| Err(())), Err(()));
+    /// let mut cell: OnceCell<u32> = OnceCell::new();
+    ///
+    /// // Failed initializers do not change the value
+    /// assert!(cell.get_mut_or_try_init(|| "not a number!".parse()).is_err());
     /// assert!(cell.get().is_none());
-    /// let value = cell.get_mut_or_try_init(|| -> Result<i32, ()> {
-    ///     Ok(92)
-    /// });
-    /// assert_eq!(value, Ok(&mut 92));
+    ///
+    /// let value = cell.get_mut_or_try_init(|| "1234".parse());
+    /// assert_eq!(value, Ok(&mut 1234));
     /// *value.unwrap() += 2;
-    /// assert_eq!(cell.get(), Some(&94))
+    /// assert_eq!(cell.get(), Some(&1236))
     /// ```
     #[unstable(feature = "once_cell_get_mut", issue = "121641")]
     pub fn get_mut_or_try_init<F, E>(&mut self, f: F) -> Result<&mut T, E>