chore: update kg-engine version to 2.2.1 for compatibility improvements

Author: dasein108

src-backend/requirements.txt

@@ -5,6 +5,6 @@ python-multipart==0.0.18
 # llama-index-core==0.12.1
 llama-parse==0.5.15
 python-dotenv==1.0.1
-kg-engine-v2==2.2.0
+kg-engine-v2==2.2.1
 # -e /Users/dasein/dev/llama_index/llama_neo4j_demo
 pydantic