tests: proxy: fix failure due to property key change in pipewire

tests/wp/proxy.c

@@ -225,7 +225,7 @@ test_proxy_node_remote_global_added (WpCore *core, WpProxy *proxy,
 
     g_assert_nonnull (props);
     g_assert_true (wp_properties_peek_dict (props) == info->props);
-    id = wp_properties_get (props, "node.id");
+    id = wp_properties_get (props, PW_KEY_OBJECT_ID);
     g_assert_nonnull (id);
     g_assert_cmpint (info->id, ==, atoi(id));
   }