Optimize refreshData in RoutingSettingActivity (#3775)

Optimized the refreshData method by clearing the existing rulesets list and adding the new items to avoid unnecessary reallocation and improve memory management.

V2rayNG/app/src/main/kotlin/com/v2ray/ang/ui/RoutingSettingActivity.kt

@@ -156,7 +156,9 @@ class RoutingSettingActivity : BaseActivity() {
     }
 
     fun refreshData() {
-        rulesets = MmkvManager.decodeRoutingRulesets() ?: mutableListOf()
+        rulesets.clear()
+        rulesets.addAll(MmkvManager.decodeRoutingRulesets() ?: mutableListOf())
         adapter.notifyDataSetChanged()
     }
+
 }