Fix: change create dataset htto api delimiter default value to r'\n' (#7434)

### What problem does this PR solve?

change create dataset delimiter default value to r'\n'

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

api/utils/api_utils.py

     if not chunk_method:
         chunk_method = "naive"
     key_mapping = {
-        "naive": {"chunk_token_num": 128, "delimiter": "\\n!?;。；！？", "html4excel": False, "layout_recognize": "DeepDOC", "raptor": {"use_raptor": False}},
+        "naive": {"chunk_token_num": 128, "delimiter": r"\n", "html4excel": False, "layout_recognize": "DeepDOC", "raptor": {"use_raptor": False}},
         "qa": {"raptor": {"use_raptor": False}},
         "tag": None,
         "resume": None,
         "laws": {"raptor": {"use_raptor": False}},
         "presentation": {"raptor": {"use_raptor": False}},
         "one": None,
-        "knowledge_graph": {"chunk_token_num": 8192, "delimiter": "\\n!?;。；！？", "entity_types": ["organization", "person", "location", "event", "time"]},
+        "knowledge_graph": {"chunk_token_num": 8192, "delimiter": r"\n", "entity_types": ["organization", "person", "location", "event", "time"]},
         "email": None,
         "picture": None,
     }

api/utils/validation_utils.py

     auto_keywords: int = Field(default=0, ge=0, le=32)
     auto_questions: int = Field(default=0, ge=0, le=10)
     chunk_token_num: int = Field(default=128, ge=1, le=2048)
-    delimiter: str = Field(default=r"\n!?;。；！？", min_length=1)
+    delimiter: str = Field(default=r"\n", min_length=1)
     graphrag: Optional[GraphragConfig] = None
     html4excel: bool = False
     layout_recognize: str = "DeepDOC"

sdk/python/test/test_http_api/test_dataset_mangement/test_create_dataset.py

         if parser_config is None:
             assert res["data"]["parser_config"] == {
                 "chunk_token_num": 128,
-                "delimiter": r"\n!?;。；！？",
+                "delimiter": r"\n",
                 "html4excel": False,
                 "layout_recognize": "DeepDOC",
                 "raptor": {"use_raptor": False},
                 "auto_keywords": 0,
                 "auto_questions": 0,
                 "chunk_token_num": 128,
-                "delimiter": r"\n!?;。；！？",
+                "delimiter": r"\n",
                 "filename_embd_weight": None,
                 "graphrag": None,
                 "html4excel": False,

sdk/python/test/test_http_api/test_file_management_within_dataset/test_update_document.py

                     "chunk_token_num": 128,
                     "layout_recognize": "DeepDOC",
                     "html4excel": False,
-                    "delimiter": "\\n!?;。；！？",
+                    "delimiter": r"\n",
                     "task_page_size": 12,
                     "raptor": {"use_raptor": False},
                 },
             else:
                 assert res["data"]["docs"][0]["parser_config"] == {
                     "chunk_token_num": 128,
-                    "delimiter": "\\n!?;。；！？",
+                    "delimiter": r"\n",
                     "html4excel": False,
                     "layout_recognize": "DeepDOC",
                     "raptor": {"use_raptor": False},