tests/Cargo: fix cargo outdated (use ffi2)

Author: Wenzel

tests/packages/hello-world/Cargo.toml

@@ -25,7 +25,7 @@ categories = [
 crate-type = ["cdylib"]
 
 [dependencies]
-ffi = "0.1.1"
+ffi2 = "0.1.0"
 
 simics = { version = "0.1.1", workspace = true }
 

tests/packages/hello-world/src/lib.rs

@@ -12,6 +12,8 @@ use simics::{
     class, interface, simics_init, FromConfObject,
 };
 
+extern crate ffi2 as ffi;
+
 #[class(name = "HelloWorld")]
 #[derive(FromConfObject, Default)]
 struct HelloWorld {