fix(lang/rust): remove unneeded dead_code allow annotation

Author: vados-cosmonic

component-model/examples/tutorial/adder/src/lib.rs

@@ -20,7 +20,6 @@ mod bindings {
 /// Struct off of which the implementation will hang
 ///
 /// The name of this struct is not significant.
-#[allow(dead_code)]
 struct AdderComponent;
 
 impl bindings::exports::docs::adder::add::Guest for AdderComponent {