Do not publish the native-c crate

Author: Kobzol

crates/native-c/Cargo.toml

@@ -7,6 +7,7 @@ Native C version of the rustc_demangle crate
 """
 license = "MIT/Apache-2.0"
 repository = "https://github.com/rust-lang/rustc-demangle"
+publish = false
 
 [lib]
 name = "rustc_demangle_native_c"