Remove AsciiChar impls

Author: Jules-Bertholet

library/core/src/ascii/ascii_char.rs

@@ -1170,26 +1170,6 @@ macro_rules! into_int_impl {
 
 into_int_impl!(u8 u16 u32 u64 u128 char);
 
-#[unstable(feature = "ascii_char", issue = "110998")]
-impl AsRef<str> for AsciiChar {
-    #[inline(always)]
-    fn as_ref(&self) -> &str {
-        self.as_str()
-    }
-}
-
-#[unstable(feature = "ascii_char", issue = "110998")]
-impl AsMut<str> for AsciiChar {
-    #[inline(always)]
-    fn as_mut(&mut self) -> &mut str {
-        let ascii_ptr: *mut [Self] = crate::slice::from_mut(self);
-        let str_ptr = ascii_ptr as *mut str;
-        // SAFETY: Each ASCII codepoint in UTF-8 is encoded as one single-byte
-        // code unit having the same value as the ASCII byte.
-        unsafe { &mut *str_ptr }
-    }
-}
-
 impl [AsciiChar] {
     /// Views this slice of ASCII characters as a UTF-8 `str`.
     #[unstable(feature = "ascii_char", issue = "110998")]