chore(pmtud): remove calls to syscall in favor of unix and windows

- syscall is deprecated and is not kept up-to-date
- each OS is inherently different hence the syscall being deprecated

internal/pmtud/ip/ipv4_windows.go

@@ -1,12 +1,10 @@
 package ip
 
 import (
-	"syscall"
-
 	"golang.org/x/sys/windows"
 )
 
-func SetIPv4HeaderIncluded(handle syscall.Handle) error {
+func SetIPv4HeaderIncluded(handle windows.Handle) error {
 	const ipHdrIncluded = windows.IP_HDRINCL
-	return syscall.SetsockoptInt(handle, syscall.IPPROTO_IP, ipHdrIncluded, 1)
+	return windows.SetsockoptInt(handle, windows.IPPROTO_IP, ipHdrIncluded, 1)
 }