Remove nightly features

Don't actually need these since we aren't defining our own pointers

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/main.rs

@@ -1,8 +1,3 @@
-// trait_upcasting - https://github.com/rust-lang/rust/issues/65991
-// stabilization in progress
-#![feature(trait_upcasting)]
-#![feature(coerce_unsized)]
-
 mod ast;
 mod builtins;
 mod compiler;