Skip flaky test_simultaneous_independent_create_set on Windows (#17468)

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

crates/uv-keyring/tests/threading.rs

@@ -167,6 +167,7 @@ async fn test_simultaneous_create_set_then_move() {
 }
 
 #[tokio::test]
+#[cfg(not(target_os = "windows"))]
 async fn test_simultaneous_independent_create_set() {
     init_logger();