style: fix typo and format code (#2618)

### What problem does this PR solve?

- Fix typo
- Remove unused import
- Format code

### Type of change

- [x] Other (please describe): typo and format

rag/app/knowledge_graph.py

@@ -1,6 +1,6 @@
 import re
 
-from graphrag.index import build_knowlege_graph_chunks
+from graphrag.index import build_knowledge_graph_chunks
 from rag.app import naive
 from rag.nlp import rag_tokenizer, tokenize_chunks
 
@@ -15,9 +15,9 @@ def chunk(filename, binary, tenant_id, from_page=0, to_page=100000,
     parser_config["layout_recognize"] = False
     sections = naive.chunk(filename, binary, from_page=from_page, to_page=to_page, section_only=True,
                            parser_config=parser_config, callback=callback)
-    chunks = build_knowlege_graph_chunks(tenant_id, sections, callback,
-                                         parser_config.get("entity_types", ["organization", "person", "location", "event", "time"])
-                                         )
+    chunks = build_knowledge_graph_chunks(tenant_id, sections, callback,
+                                          parser_config.get("entity_types", ["organization", "person", "location", "event", "time"])
+                                          )
     for c in chunks: c["docnm_kwd"] = filename
 
     doc = {