net/http: remove check for null bytes in Dir.Open()

The syscall package checks for null bytes now.
This was added in https://codereview.appspot.com/6458050

Change-Id: I59a2fed3757a25b85e2668905ff5cf2ec8c3a0d3
Reviewed-on: https://go-review.googlesource.com/34978Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/net/http/fs.go

@@ -34,8 +34,7 @@ import (
 type Dir string
 
 func (d Dir) Open(name string) (File, error) {
-	if filepath.Separator != '/' && strings.ContainsRune(name, filepath.Separator) ||
-		strings.Contains(name, "\x00") {
+	if filepath.Separator != '/' && strings.ContainsRune(name, filepath.Separator) {
 		return nil, errors.New("http: invalid character in file path")
 	}
 	dir := string(d)