Summary:
Recent update of pybind version from PyTorch (pytorch/pytorch#46415) created compatibility issue, resulting in mysterious errors like
```
__________________ TestRemoveException.test_remove_exceptions __________________
self = <tests.functionality.remove_exceptions_test.TestRemoveException testMethod=test_remove_exceptions>

    def test_remove_exceptions(self):
        """Test Glow's removeExceptions JIT pass"""

        foo_jit = torch.jit.script(foo)
        graph = foo_jit.graph
        assert graph_contains_str(graph, "prim::RaiseException")
>       torch_glow.removeExceptions_(graph)
E       TypeError: removeExceptions_(): incompatible function arguments. The following argument types are supported:
E           1. (arg0: torch::jit::Graph) -> None
```
This PR aligns the pybind11 versions in glow and pytorch, hence fixing the issue.

Documentation:

[Optional Fixes #issue]

Pull Request resolved: pytorch#5067

Test Plan: CI

Reviewed By: hl475

Differential Revision: D24912990

Pulled By: yinghai

fbshipit-source-id: ed22a8c70b51638fa11a5a172b93339563152869