Simplify WinError cfg

Author: bdbai

library/std/src/sys/pal/windows/os.rs

@@ -6,7 +6,7 @@
 mod tests;
 
 use super::api;
-#[cfg(any(not(target_vendor = "uwp"), target_vendor = "win7"))]
+#[cfg(not(target_vendor = "uwp"))]
 use super::api::WinError;
 use super::to_u16s;
 use crate::error::Error as StdError;