test: update new test to expect main instead of module

Update test case that landed after this PR was created, in
https://github.com/rustwasm/wasm-pack/pull/1061, to expect main attribute in
package.json instead of module attribute.

tests/all/manifest.rs

@@ -346,7 +346,7 @@ fn it_creates_a_package_json_with_npm_dependencies_provided_by_wasm_bindgen() {
         pkg.repository.url,
         "https://github.com/rustwasm/wasm-pack.git"
     );
-    assert_eq!(pkg.module, "js_hello_world.js");
+    assert_eq!(pkg.main, "js_hello_world.js");
 
     let actual_files: HashSet<String> = pkg.files.into_iter().collect();
     let expected_files: HashSet<String> = [