chore: Fixes generate_image sample

PiperOrigin-RevId: 793725452

Author: Jacksunwei

contributing/samples/generate_image/agent.py

@@ -13,7 +13,7 @@
 # limitations under the License.
 
 from google.adk import Agent
-from google.adk.tools.load_artifacts_tool import load_artifacts
+from google.adk.tools import load_artifacts
 from google.adk.tools.tool_context import ToolContext
 from google.genai import Client
 from google.genai import types