fix(safety): remove unused max_risk_level import

Resolve flake8 F401 in UnsafeLocalCodeExecutor.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: Violet2314

trpc_agent_sdk/code_executors/local/_unsafe_local_code_executor.py

@@ -115,7 +115,6 @@ async def execute_code(self, invocation_context: InvocationContext,
                 code_blocks = [CodeBlock(code=input_data.code, language="python")]
             # Scan each block with its own language so bash is not missed.
             from trpc_agent_sdk.safety import RiskLevel
-            from trpc_agent_sdk.safety import max_risk_level
 
             _ORDER = {
                 RiskLevel.NONE: 0,