fix typo

Co-authored-by: kennytm <kennytm@gmail.com>

Author: RalfJung

library/core/src/ptr/mod.rs

@@ -1545,7 +1545,7 @@ fnptr_impls_args! { A, B, C, D, E, F, G, H, I, J, K, L }
 /// assert_eq!(unsafe { raw_f2.read_unaligned() }, 2);
 /// ```
 ///
-/// See [`addr_of_mut`] for how to create a pointer to ininitialized data.
+/// See [`addr_of_mut`] for how to create a pointer to unininitialized data.
 /// Doing that with `addr_of` would not make much sense since one could only
 /// read the data, and that would be Undefined Behavior.
 #[stable(feature = "raw_ref_macros", since = "1.51.0")]