Fix flake8 error: remove unnecessary global declaration

Co-authored-by: gkorland <753206+gkorland@users.noreply.github.com>

Author: Copilot

api/llm.py

@@ -235,8 +235,6 @@ def _define_ontology() -> Ontology:
 ontology = _define_ontology()
 
 def _create_kg_agent(repo_name: str):
-    global ontology
-
     model_name = os.getenv('MODEL_NAME', 'gemini/gemini-2.0-flash')
 
     model = LiteModel(model_name)