Update MX records format in huykhang.json

Removed priority numbers from MX records in JSON.

domains/huykhang.json

@@ -13,8 +13,8 @@
       "185.199.111.153"
     ],
     "MX": [
-      "10 mx1.improvmx.com",
-      "20 mx2.improvmx.com"
+      "mx1.improvmx.com",
+      "mx2.improvmx.com"
     ],
     "TXT": "v=spf1 include:spf.improvmx.com ~all"
   }