fix(crypto-nodejs): OlmMachine.new effectively raises an error.

Returning an `napi::Error` doesn't raise it. We must return a
`Result<_, napi::Error>` to ensure `napi` will raise the error as
expected.

crates/matrix-sdk-crypto-nodejs/src/machine.rs

@@ -62,8 +62,10 @@ impl OlmMachine {
     /// asynchronous. Please use the `finalize` method.
     #[napi(constructor)]
     #[allow(clippy::new_ret_no_self)]
-    pub fn new() -> napi::Error {
-        napi::Error::from_reason("To build an `OldMachine`, please use the `initialize` method")
+    pub fn new() -> Result<(), napi::Error> {
+        Err(napi::Error::from_reason(
+            "To build an `OldMachine`, please use the `initialize` method",
+        ))
     }
 
     /// The unique user ID that owns this `OlmMachine` instance.

crates/matrix-sdk-crypto-nodejs/tests/machine.test.js

@@ -0,0 +1,7 @@
+const { OlmMachine } = require('../');
+
+describe(OlmMachine.name, () => {
+    test('cannot be instantiated', () => {
+        expect(() => { new OlmMachine() }).toThrow();
+    });
+});