rust: sort uml documentation arch support table

The arch_support table was not sorted alphabetically.
Sorts the table properly.

Fixes: 0438aadf

 ("rust: arch/um: Add support for CONFIG_RUST under x86_64 UML")
Link: https://lore.kernel.org/rust-for-linux/CANiq72nXMsnUsJNZOG-QZiCVOqa9dRUSMc4RAS3ExLZNJ7VhHg@mail.gmail.com
Reported-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Signed-off-by: Thomas Bamelis <thomas@bamelis.dev>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>