Remove redundant #![allow()] from main_native (#1703)

`main_native.rs` is a module of `main.rs`, so the `#![allow()]`s in the
latter apply to the former automatically.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

src/main_native.rs

@@ -1,16 +1,3 @@
-#![allow(
-    clippy::collapsible_else_if,
-    clippy::collapsible_if,
-    clippy::implicit_hasher,
-    clippy::match_same_arms,
-    clippy::missing_errors_doc,
-    clippy::missing_panics_doc,
-    clippy::module_name_repetitions,
-    clippy::must_use_candidate,
-    clippy::similar_names,
-    clippy::too_many_lines
-)]
-
 use std::io::{self};
 use std::path::{Path, PathBuf};
 use std::process::ExitCode;