windows: don't check non-existent return code in GetStartupInfo

Same as CL 520275 did in package syscall.

For golang/go#31316

Change-Id: Ie9d8fed7f40b9e562534d5e91488b4ba1ac44f34
Reviewed-on: https://go-review.googlesource.com/c/sys/+/520295
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
diff --git a/windows/zsyscall_windows.go b/windows/zsyscall_windows.go
index 1c31758..5c38558 100644
--- a/windows/zsyscall_windows.go
+++ b/windows/zsyscall_windows.go
@@ -2370,11 +2370,8 @@
 	return
 }
 
-func GetStartupInfo(startupInfo *StartupInfo) (err error) {
-	r1, _, e1 := syscall.Syscall(procGetStartupInfoW.Addr(), 1, uintptr(unsafe.Pointer(startupInfo)), 0, 0)
-	if r1 == 0 {
-		err = errnoErr(e1)
-	}
+func getStartupInfo(startupInfo *StartupInfo) {
+	syscall.Syscall(procGetStartupInfoW.Addr(), 1, uintptr(unsafe.Pointer(startupInfo)), 0, 0)
 	return
 }