feat: drop ipv6 test due to server down

ip/ipv6.go

@@ -1,28 +1,3 @@
 package ip
 
-import (
-	"context"
-	"net/http"
-	"time"
-
-	"github.com/RomiChan/syncx"
-)
-
-var IsIPv6Available = syncx.Lazy[bool]{Init: func() bool {
-	ctx, cancel := context.WithTimeout(context.Background(), 4*time.Second)
-	defer cancel()
-	req, err := http.NewRequestWithContext(ctx, "GET", "http://v6.ipv6-test.com/json/widgetdata.php?callback=?", nil)
-	if err != nil {
-		return false
-	}
-	resp, err := http.DefaultClient.Do(req)
-	if err != nil {
-		return false
-	}
-	_ = resp.Body.Close()
-	return true
-}}
-
-func init() {
-	go IsIPv6Available.Get()
-}
+var IsIPv6Available = true