Use relative links instead of linking to doc.rust-lang.org when possible

Author: GuillaumeGomez

library/core/src/hash/sip.rs

@@ -38,7 +38,7 @@ struct SipHasher24 {
 /// SipHash is a general-purpose hashing function: it runs at a good
 /// speed (competitive with Spooky and City) and permits strong _keyed_
 /// hashing. This lets you key your hash tables from a strong RNG, such as
-/// [`rand::os::OsRng`](https://doc.rust-lang.org/rand/rand/os/struct.OsRng.html).
+/// [`rand::os::OsRng`](https://docs.rs/rand/latest/rand/rngs/struct.OsRng.html).
 ///
 /// Although the SipHash algorithm is considered to be generally strong,
 /// it is not intended for cryptographic purposes. As such, all

library/core/src/mem/maybe_uninit.rs

@@ -865,7 +865,7 @@ impl<T> MaybeUninit<T> {
     ///
     /// For instance, you cannot [`Read`] into an uninitialized buffer:
     ///
-    /// [`Read`]: https://doc.rust-lang.org/std/io/trait.Read.html
+    /// [`Read`]: ../../std/io/trait.Read.html
     ///
     /// ```rust,no_run
     /// use std::{io, mem::MaybeUninit};