Fix some ruff issues in code

tests/test_agent.py

@@ -99,7 +99,7 @@ class TestExecuteToolCall:
                 "arguments": '{"folder_name": 123}',  # Wrong type
             },
         }
-        result = agent._execute_tool_call(tool_call)
+        agent._execute_tool_call(tool_call)
 
         mem = get_memory()
         assert len(mem.episodic.recent_errors) > 0
@@ -187,7 +187,7 @@ class TestStep:
         mock_llm.complete = Mock(side_effect=mock_complete)
         agent = Agent(llm=mock_llm, max_tool_iterations=3)
 
-        response = agent.step("Do something")
+        agent.step("Do something")
 
         assert call_count[0] == 4
 
@@ -278,6 +278,6 @@ class TestAgentIntegration:
         mock_llm.complete = Mock(side_effect=mock_complete)
         agent = Agent(llm=mock_llm)
 
-        response = agent.step("List my downloads and movies")
+        agent.step("List my downloads and movies")
 
         assert call_count[0] == 3