fix(接口测试):使XPath断言规则的表达式能接收更长的字符 (#1661)

Co-authored-by: 黎龙鑫 <lilongxinya@163.com>

frontend/src/business/components/api/definition/components/assertion/ApiAssertionXPath2.vue

@@ -2,7 +2,7 @@
   <div>
     <el-row :gutter="10" type="flex" justify="space-between" align="middle">
       <el-col>
-        <el-input :disabled="isReadOnly" v-model="xPath2.expression" maxlength="200" size="small" show-word-limit
+        <el-input :disabled="isReadOnly" v-model="xPath2.expression" maxlength="500" size="small" show-word-limit
                   :placeholder="$t('api_test.request.extract.xpath_expression')"/>
       </el-col>
       <el-col class="assertion-btn">