Go: fix Baidu rerank issue (#14742)

### What problem does this PR solve?

top_n is missing

### Type of change

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

Signed-off-by: Jin Hai <haijin.chn@gmail.com>

internal/entity/models/baidu.go

@@ -520,10 +520,16 @@ func (b *BaiduModel) Rerank(modelName *string, query string, documents []string,
 
 	url := fmt.Sprintf("%s/%s", strings.TrimSuffix(b.BaseURL[region], "/"), b.URLSuffix.Rerank)
 
+	var topN = rerankConfig.TopN
+	if rerankConfig.TopN == 0 {
+		topN = len(documents)
+	}
+
 	reqBody := map[string]interface{}{
 		"model":     *modelName,
 		"query":     query,
 		"documents": documents,
+		"top_n":     topN,
 	}
 
 	jsonData, err := json.Marshal(reqBody)