Revert "net: prevent udp_test.v from running on windows without -d network"

This reverts commit 3526bc3d19.

vlib/net/udp_test.v

@@ -1,13 +1,5 @@
 import net
 
-fn testsuite_begin() {
-	$if windows {
-		$if !network ? {
-			exit(0)
-		}
-	}
-}
-
 fn echo_server(mut c net.UdpConn) {
 	for {
 		mut buf := []byte{len: 100, init: 0}
@@ -64,3 +56,7 @@ fn test_udp() {
 
 	l.close() or { }
 }
+
+fn main() {
+	test_udp()
+}