fix: rename "Regular user" to "No subscription" in legend

The gray color in the referral network legend represents users without
a subscription, not "regular/organic" users. Updated labels in all
4 locales (en, ru, fa, zh) to reflect this.

src/locales/fa.json

@@ -1087,7 +1087,7 @@
         "title": "راهنما",
         "fillTitle": "اشتراک",
         "borderTitle": "نقش ارجاع‌دهنده",
-        "regularUser": "کاربر عادی",
+        "regularUser": "بدون اشتراک",
         "activeReferrer": "ارجاع‌دهنده فعال",
         "partner": "شریک",
         "topReferrer": "ارجاع‌دهنده برتر (+۱۰)",