lib docs: fix typo

Author: RalfJung

library/core/src/ptr/mod.rs

@@ -1769,7 +1769,7 @@ pub(crate) const unsafe fn align_offset<T: Sized>(p: *const T, a: usize) -> usiz
 /// (which is what the `PartialEq for &T` implementation does).
 ///
 /// When comparing wide pointers, both the address and the metadata are tested for equality.
-/// However, note that comparing trait object pointers (`*const dyn Trait`) is unrealiable: pointers
+/// However, note that comparing trait object pointers (`*const dyn Trait`) is unreliable: pointers
 /// to values of the same underlying type can compare inequal (because vtables are duplicated in
 /// multiple codegen units), and pointers to values of *different* underlying type can compare equal
 /// (since identical vtables can be deduplicated within a codegen unit).