Don't include unistd.h in sconnect for windows

The platform doesn't support it

Reviewed-by: Nicola Tuveri <nic.tuv@gmail.com>
Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Paul Dale <ppzgs1@gmail.com>
Reviewed-by: Tom Cosgrove <tom.cosgrove@arm.com>
(Merged from https://github.com/openssl/openssl/pull/24047)

demos/bio/sconnect.c

@@ -16,11 +16,16 @@
  */
 #include <stdio.h>
 #include <stdlib.h>
-#include <unistd.h>
 #include <string.h>
 #include <errno.h>
 #include <openssl/err.h>
 #include <openssl/ssl.h>
+#if !defined(OPENSSL_SYS_WINDOWS)
+#include <unistd.h>
+#else
+#include <windows.h>
+# define sleep(x) Sleep(x*1000)
+#endif
 
 #define HOSTPORT "localhost:4433"
 #define CAFILE "root.pem"