fix(性能测试): 修复性能测试中重复名称的提示

--bug=1008230 --user=刘瑞斌 【性能测试】创建性能测试，提示 “测试计划名称已存在” https://www.tapd.cn/55049933/s/1072645

backend/src/main/java/io/metersphere/performance/service/PerformanceTestService.java

@@ -237,7 +237,7 @@ public class PerformanceTestService {
                 criteria.andIdNotEqualTo(request.getId());
             }
             if (loadTestMapper.selectByExample(example).size() > 0) {
-                MSException.throwException(Translator.get("plan_name_already_exists"));
+                MSException.throwException(Translator.get("api_test_name_already_exists"));
             }
         }
     }