fix: ensure unique tag IDs when creating new document tags

--bug=1062908 --user=刘瑞斌 【知识库】文档标签设置，添加标签时，重复选择相同的标签，添加报错 https://www.tapd.cn/62980211/s/1789052

apps/knowledge/serializers/document.py

@@ -1475,7 +1475,7 @@ class DocumentSerializers(serializers.Serializer):
                     id=uuid.uuid7(),
                     document_id=document_id,
                     tag_id=tag_id
-                ) for tag_id in tag_ids if tag_id not in existing_tag_ids
+                ) for tag_id in set(tag_ids) if tag_id not in existing_tag_ids
             ]
             if new_tags:
                 QuerySet(DocumentTag).bulk_create(new_tags)