feat(vpcs_tools_netmiko): update Nornir import to use core module

Update the import statement for Nornir from `nornir.core.nornir` to `nornir.core` to align with the latest Nornir library structure and avoid potential import errors. This ensures compatibility with updated Nornir versions.

gns3server/agent/gns3_copilot/tools_v2/vpcs_tools_netmiko.py

@@ -37,7 +37,7 @@ from langchain.tools import BaseTool
 from langchain_core.callbacks import CallbackManagerForToolRun
 from netmiko.exceptions import ReadTimeout
 from nornir import InitNornir
-from nornir.core.nornir import Nornir
+from nornir.core import Nornir
 from nornir.core.task import AggregatedResult
 from nornir.core.task import Result
 from nornir.core.task import Task