refactor: adapt wrong imports in tck and sample

samples/hello_world_agent.py

@@ -1,37 +1,35 @@
 import asyncio
 import contextlib
 import logging
 
 import grpc
 import uvicorn
 
 from fastapi import FastAPI
 
 from a2a.compat.v0_3 import a2a_v0_3_pb2_grpc
 from a2a.compat.v0_3.grpc_handler import CompatGrpcHandler
 from a2a.server.agent_execution.agent_executor import AgentExecutor
 from a2a.server.agent_execution.context import RequestContext
 from a2a.server.events.event_queue import EventQueue
 from a2a.server.request_handlers import GrpcHandler
-from a2a.server.request_handlers.default_request_handler import (
-    DefaultRequestHandler,
-)
+from a2a.server.request_handlers import DefaultRequestHandler
 from a2a.server.routes import (
     create_agent_card_routes,
     create_jsonrpc_routes,
     create_rest_routes,
 )
 from a2a.server.tasks.inmemory_task_store import InMemoryTaskStore
 from a2a.server.tasks.task_updater import TaskUpdater
 from a2a.types import (
     AgentCapabilities,
     AgentCard,
     AgentInterface,
     AgentProvider,
     AgentSkill,
     Part,
     a2a_pb2_grpc,
 )
 
 
 logger = logging.getLogger(__name__)

tck/sut_agent.py

@@ -17,9 +17,7 @@
 from a2a.server.agent_execution.agent_executor import AgentExecutor
 from a2a.server.agent_execution.context import RequestContext
 from a2a.server.events.event_queue import EventQueue
-from a2a.server.request_handlers.default_request_handler import (
-    DefaultRequestHandler,
-)
+from a2a.server.request_handlers import DefaultRequestHandler
 from a2a.server.request_handlers.grpc_handler import GrpcHandler
 from a2a.server.routes import (
     create_agent_card_routes,