refactor: add deletion of ApplicationKnowledgeMapping entries when knowledge is deleted

--bug=1058030 --user=刘瑞斌 【知识库】知识库已关联应用-删除报错 https://www.tapd.cn/62980211/s/1722902

Author: liuruibin

apps/knowledge/serializers/knowledge.py

@@ -409,6 +409,7 @@ def delete(self):
             QuerySet(Paragraph).filter(knowledge=knowledge).delete()
             QuerySet(Problem).filter(knowledge=knowledge).delete()
             QuerySet(WorkspaceUserResourcePermission).filter(target=knowledge.id).delete()
+            QuerySet(ApplicationKnowledgeMapping).filter(knowledge_id=knowledge.id).delete()
             knowledge.delete()
             delete_embedding_by_knowledge(self.data.get('knowledge_id'))
             return True