only remove lane_idx if exist in closed_lanes

[piliwilliam0306]

Bug fix

Fixed bug

If lane_idx not in closed_lanes, it would show below error:

[fleet_adapter-14] Traceback (most recent call last):
[fleet_adapter-14]   File "/home/will/humble_harmonic/rmf_ws/install/rmf_demos_fleet_adapter/lib/rmf_demos_fleet_adapter/fleet_adapter", line 33, in <module>
[fleet_adapter-14]     sys.exit(load_entry_point('rmf-demos-fleet-adapter==2.5.0', 'console_scripts', 'fleet_adapter')())
[fleet_adapter-14]   File "/home/will/humble_harmonic/rmf_ws/install/rmf_demos_fleet_adapter/lib/python3.10/site-packages/rmf_demos_fleet_adapter/fleet_adapter.py", line 181, in main
[fleet_adapter-14]     rclpy_executor.spin()
[fleet_adapter-14]   File "/opt/ros/humble/local/lib/python3.10/dist-packages/rclpy/executors.py", line 294, in spin
[fleet_adapter-14]     self.spin_once()
[fleet_adapter-14]   File "/opt/ros/humble/local/lib/python3.10/dist-packages/rclpy/executors.py", line 739, in spin_once
[fleet_adapter-14]     self._spin_once_impl(timeout_sec)
[fleet_adapter-14]   File "/opt/ros/humble/local/lib/python3.10/dist-packages/rclpy/executors.py", line 736, in _spin_once_impl
[fleet_adapter-14]     raise handler.exception()
[fleet_adapter-14]   File "/opt/ros/humble/local/lib/python3.10/dist-packages/rclpy/task.py", line 239, in __call__
[fleet_adapter-14]     self._handler.send(None)
[fleet_adapter-14]   File "/opt/ros/humble/local/lib/python3.10/dist-packages/rclpy/executors.py", line 437, in handler
[fleet_adapter-14]     await call_coroutine(entity, arg)
[fleet_adapter-14]   File "/opt/ros/humble/local/lib/python3.10/dist-packages/rclpy/executors.py", line 362, in _execute_subscription
[fleet_adapter-14]     await await_or_execute(sub.callback, msg)
[fleet_adapter-14]   File "/opt/ros/humble/local/lib/python3.10/dist-packages/rclpy/executors.py", line 107, in await_or_execute
[fleet_adapter-14]     return callback(*args)
[fleet_adapter-14]   File "/home/will/humble_harmonic/rmf_ws/install/rmf_demos_fleet_adapter/lib/python3.10/site-packages/rmf_demos_fleet_adapter/fleet_adapter.py", line 459, in lane_request_cb
[fleet_adapter-14]     closed_lanes.remove(lane_idx)
[fleet_adapter-14] KeyError: 2

This PR will check if lane_idx in closed_lanes before calling closed_lanes.remove(lane_idx)

[Yadunund]

Thanks for the fix!

[Yadunund]

@Mergifyio backport jazzy humble