Remove default_free_fn feature

Signed-off-by: Yuki Okushi <jtitor@2k36.org>

Author: JohnTitor

core/src/default.rs

@@ -133,51 +133,6 @@ pub trait Default: Sized {
     fn default() -> Self;
 }
 
-/// Return the default value of a type according to the `Default` trait.
-///
-/// The type to return is inferred from context; this is equivalent to
-/// `Default::default()` but shorter to type.
-///
-/// For example:
-/// ```
-/// #![feature(default_free_fn)]
-///
-/// use std::default::default;
-///
-/// #[derive(Default)]
-/// struct AppConfig {
-///     foo: FooConfig,
-///     bar: BarConfig,
-/// }
-///
-/// #[derive(Default)]
-/// struct FooConfig {
-///     foo: i32,
-/// }
-///
-/// #[derive(Default)]
-/// struct BarConfig {
-///     bar: f32,
-///     baz: u8,
-/// }
-///
-/// fn main() {
-///     let options = AppConfig {
-///         foo: default(),
-///         bar: BarConfig {
-///             bar: 10.1,
-///             ..default()
-///         },
-///     };
-/// }
-/// ```
-#[unstable(feature = "default_free_fn", issue = "73014")]
-#[must_use]
-#[inline]
-pub fn default<T: Default>() -> T {
-    Default::default()
-}
-
 /// Derive macro generating an impl of the trait `Default`.
 #[rustc_builtin_macro(Default, attributes(default))]
 #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]