fix(接口测试): 修复生成JMX文件提取步骤默认匹配多条被勾选问题

--bug=1014849 --user=赵勇 【接口测试】github#15751，场景导出JMX或者转成性能测试后，提取默认勾选上了 “匹配多条” https://www.tapd.cn/55049933/s/1201389

backend/src/main/java/io/metersphere/api/dto/definition/request/extract/MsExtract.java

@@ -165,7 +165,7 @@ public class MsExtract extends MsTestElement {
         extractor.setProperty(TestElement.GUI_CLASS, SaveService.aliasToClass("JSONPostProcessorGui"));
         extractor.setRefNames(extractJSONPath.getVariable());
         extractor.setJsonPathExpressions(extractJSONPath.getExpression());
-        extractor.setComputeConcatenation(true);
+        extractor.setComputeConcatenation(extractJSONPath.isMultipleMatching());
         if (extractJSONPath.isMultipleMatching()) {
             extractor.setMatchNumbers("-1");
         }