docs: fix some spelling mistakes (#633)

Author: mxsm

src/buf/uninit_slice.rs

@@ -168,7 +168,7 @@ impl UninitSlice {
     ///
     /// The caller **must not** read from the referenced memory and **must not** write
     /// **uninitialized** bytes to the slice either. This is because `BufMut` implementation
-    /// that created the `UninitSlice` knows which parts are initialized. Writing uninitalized
+    /// that created the `UninitSlice` knows which parts are initialized. Writing uninitialized
     /// bytes to the slice may cause the `BufMut` to read those bytes and trigger undefined
     /// behavior.
     ///

src/bytes_mut.rs

@@ -1684,7 +1684,7 @@ fn invalid_ptr<T>(addr: usize) -> *mut T {
 /// self.ptr.as_ptr().offset_from(ptr) as usize;
 /// ```
 ///
-/// But due to min rust is 1.39 and it is only stablised
+/// But due to min rust is 1.39 and it is only stabilized
 /// in 1.47, we cannot use it.
 #[inline]
 fn offset_from(dst: *mut u8, original: *mut u8) -> usize {