Fix: typo (#281)

constant/adapters.go

@@ -103,6 +103,6 @@ func (at AdapterType) String() string {
 	case LoadBalance:
 		return "LoadBalance"
 	default:
-		return "Unknow"
+		return "Unknown"
 	}
 }

constant/rule.go

@@ -36,7 +36,7 @@ func (rt RuleType) String() string {
 	case MATCH:
 		return "MATCH"
 	default:
-		return "Unknow"
+		return "Unknown"
 	}
 }