Part of #29365
explain that std::mem::drop in prelude will invoke Drop
change "prelude" -> "the prelude"; change links to reference-style
move link references to links' section
///
/// After this function is over, the memory of `self` will be deallocated.
///
+ /// This function cannot be called explicitly. This is compiler error
+ /// [0040]. However, the [`std::mem::drop`] function in the prelude can be
+ /// used to call the argument's `Drop` implementation.
+ ///
+ /// [0040]: https://doc.rust-lang.org/error-index.html#E0040
+ /// [`std::mem::drop`]: https://doc.rust-lang.org/std/mem/fn.drop.html
+ ///
/// # Panics
///
/// Given that a `panic!` will call `drop()` as it unwinds, any `panic!` in