Updated golang/x/net. Also updated golang.org/x/sys, as required by

hack/lint-dependencies.sh.

vendor/golang.org/x/sys/unix/syscall_dragonfly.go

@@ -129,23 +129,8 @@ func Accept4(fd, flags int) (nfd int, sa Sockaddr, err error) {
 	return
 }
 
-const ImplementsGetwd = true
-
 //sys	Getcwd(buf []byte) (n int, err error) = SYS___GETCWD
 
-func Getwd() (string, error) {
-	var buf [PathMax]byte
-	_, err := Getcwd(buf[0:])
-	if err != nil {
-		return "", err
-	}
-	n := clen(buf[:])
-	if n < 1 {
-		return "", EINVAL
-	}
-	return string(buf[:n]), nil
-}
-
 func Getfsstat(buf []Statfs_t, flags int) (n int, err error) {
 	var _p0 unsafe.Pointer
 	var bufsize uintptr