Rollup merge of #108356 - gftea:master, r=workingjubilee

improve doc test for UnsafeCell::raw_get

improve docs of public API `UnsafeCell::raw_get`

library/core/src/cell.rs

@@ -2100,6 +2100,8 @@ impl<T: ?Sized> UnsafeCell<T> {
     ///
     /// let m = MaybeUninit::<UnsafeCell<i32>>::uninit();
     /// unsafe { UnsafeCell::raw_get(m.as_ptr()).write(5); }
+    /// // avoid below which references to uninitialized data
+    /// // unsafe { UnsafeCell::get(&*m.as_ptr()).write(5); }
     /// let uc = unsafe { m.assume_init() };
     ///
     /// assert_eq!(uc.into_inner(), 5);