Prefer __nodiscard to __wur for readability.

[[nodiscard]] is the C++17 and C23 spelling, and even if you're not familiar with that yet, "wur" doesn't mean anything to anyone who isn't a libc maintainer!

Change-Id: I9a63b1e438a347a56535b01d6d05532ee052bcea
diff --git a/libc/include/sys/cdefs.h b/libc/include/sys/cdefs.h
index 5d1718e..4aea97a 100644
--- a/libc/include/sys/cdefs.h
+++ b/libc/include/sys/cdefs.h
@@ -140,7 +140,8 @@
 #define	__predict_true(exp)	__builtin_expect((exp) != 0, 1)
 #define	__predict_false(exp)	__builtin_expect((exp) != 0, 0)
 
-#define __wur __attribute__((__warn_unused_result__))
+#define __nodiscard __attribute__((__warn_unused_result__))
+#define __wur __nodiscard
 
 #define __errorattr(msg) __attribute__((__unavailable__(msg)))
 #define __warnattr(msg) __attribute__((__deprecated__(msg)))