models: OpticsPhysicalChannelsDict value should be a list

In all of the base [1], drivers and test fixture implementations of `NetworkDriver.get_optics()`, the return value `.[intf_name]["physical_channels"]["channels"]` is a list of dictionaries (specifically, a list of `OpticsPerChannelDict`). However, in the current model, it is listed as a single `OpticsPerChannelDict`. I believe that this was a mistake.

[1]: https://github.com/napalm-automation/napalm/blob/5bc2bfc40f7bf182eaf0c91a6752d25d4f966350/napalm/base/base.py#L1557 (base)
[2]: https://github.com/napalm-automation/napalm/blob/5bc2bfc40f7bf182eaf0c91a6752d25d4f966350/napalm/eos/eos.py#L2017 (eos)
[3]: https://github.com/napalm-automation/napalm/blob/5bc2bfc40f7bf182eaf0c91a6752d25d4f966350/napalm/ios/ios.py#L934 (ios)
[4]: https://github.com/napalm-automation/napalm/blob/5bc2bfc40f7bf182eaf0c91a6752d25d4f966350/napalm/junos/junos.py#L2404 (junos)
[5]: https://github.com/napalm-automation/napalm/blob/5bc2bfc40f7bf182eaf0c91a6752d25d4f966350/napalm/nxos_ssh/nxos_ssh.py#L1634 (nxos_ssh)
[6]: https://github.com/napalm-automation/napalm/blob/5bc2bfc40f7bf182eaf0c91a6752d25d4f966350/test/ios/mocked_data/test_get_optics/normal/expected_result.json#L4 (mocked data)

Author: yzgyyang

napalm/base/models.py

@@ -399,7 +399,7 @@
 )
 
 OpticsPhysicalChannelsDict = TypedDict(
-    "OpticsPhysicalChannelsDict", {"channels": OpticsPerChannelDict}
+    "OpticsPhysicalChannelsDict", {"channels": List[OpticsPerChannelDict]}
 )
 
 OpticsDict = TypedDict("OpticsDict", {"physical_channels": OpticsPhysicalChannelsDict})