[Core] Fix broken dashboard cluster page when there are dead nodes

[jjyao]

Why are these changes needed?

After #47367, nodes are updated through pub-sub and for dead node there is no state_snapshot set anymore. The datacenter.py tries to access it even for dead node which leads to KeyError:

File "/local_disk0/.ephemeral_nfs/envs/pythonEnv-8ac7e00d-2d10-430a-b39d-ad4447d3a5ed/lib/python3.11/site-packages/ray/dashboard/datacenter.py", line 150, in get_node_info
    node_info["status"] = node["stateSnapshot"]["state"]
                          ~~~~^^^^^^^^^^^^^^^^^
  File "/local_disk0/.ephemeral_nfs/envs/pythonEnv-8ac7e00d-2d10-430a-b39d-ad4447d3a5ed/lib/python3.11/site-packages/ray/dashboard/utils.py", line 435, in __getitem__
    proxy = self._proxy[item] = make_immutable(self._dict[item])
                                               ~~~~~~~~~~^^^^^^
KeyError: 'stateSnapshot'

It turns out the problematic line of code is dead code so this PR just removes it.

Related issue number

Closes #47668

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  • I've added any new APIs to the API Reference. For example, if I added a
    method in Tune, I've added it in doc/source/tune/api/ under the
    corresponding .rst file.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[WeichenXu123]

LGTM.