Don't re-export private/unstable ArgumentV1 from alloc.

Author: m-ou-se

library/alloc/src/fmt.rs

@@ -558,7 +558,7 @@ pub use core::fmt::Alignment;
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::fmt::Error;
 #[stable(feature = "rust1", since = "1.0.0")]
-pub use core::fmt::{write, ArgumentV1, Arguments};
+pub use core::fmt::{write, Arguments};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::fmt::{Binary, Octal};
 #[stable(feature = "rust1", since = "1.0.0")]