fix: remove Top K in retrieval testing #770 and if the document parsing fails, the error message returned by the backend is displayed (#782)

### What problem does this PR solve?

fix: remove Top K in retrieval testing  #770
fix: if the document parsing fails, the error message returned by the
backend is displayed.

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

web/src/pages/add-knowledge/components/knowledge-testing/testing-control/index.tsx

@@ -1,5 +1,5 @@
 import SimilaritySlider from '@/components/similarity-slider';
-import { Button, Card, Divider, Flex, Form, Input, Slider } from 'antd';
+import { Button, Card, Divider, Flex, Form, Input } from 'antd';
 import { FormInstance } from 'antd/lib';
 
 import { useTranslate } from '@/hooks/commonHooks';
@@ -9,7 +9,6 @@ import styles from './index.less';
 type FieldType = {
   similarity_threshold?: number;
   vector_similarity_weight?: number;
-  top_k?: number;
   question: string;
 };
 
@@ -36,22 +35,8 @@ const TestingControl = ({ form, handleTesting }: IProps) => {
       <p>{t('testingDescription')}</p>
       <Divider></Divider>
       <section>
-        <Form
-          name="testing"
-          layout="vertical"
-          form={form}
-          initialValues={{
-            top_k: 1024,
-          }}
-        >
+        <Form name="testing" layout="vertical" form={form}>
           <SimilaritySlider isTooltipShown></SimilaritySlider>
-          <Form.Item<FieldType>
-            label="Top K"
-            name={'top_k'}
-            tooltip={t('topKTip')}
-          >
-            <Slider marks={{ 0: 0, 2048: 2048 }} max={2048} />
-          </Form.Item>
           <Card size="small" title={t('testText')}>
             <Form.Item<FieldType>
               name={'question'}