Update alchemy gufe import

[kaminow]

A recent update to gufe changed where the JSONCodec class lives, update import to new location. Fixes #101.

[mariacm12]

Thanks! The import error is gone.
Non-blocking: Now there's another error:

 def test_plan_from_names(tyk2_ligands, tyk2_small_custom_network):
        """Make sure we can plan a network using the names of the ligands."""
        edges = extract_custom_ligand_network(tyk2_small_custom_network)
        planner = NetworkPlanner(network_planning_method=CustomNetworkPlanner(edges=edges))
        network = planner.generate_network(ligands=tyk2_ligands).to_ligand_network()
        # make sure the edges are as we expect
        for edge in network.edges:
>           assert (edge.componentA.name, edge.componentB.name) in edges
E           AssertionError: assert ('', '') in [('lig_ejm_46', 'lig_jmc_23'), ('lig_jmc_23', 'lig_jmc_28'), ('lig_ejm_31', 'lig_ejm_46')]

drugforge-alchemy/drugforge/alchemy/tests/test_fec_schema.py:117: AssertionError

And another with cinnabar on ubuntu:

E       AttributeError: 'FEMap' object has no attribute 'graph'

drugforge-alchemy/drugforge/alchemy/cli/utils.py:304: AttributeError

Not sure if we want to try and fix it in this PR or make a new one.

[kaminow]

I feel like those should probably go in a different PR, but I'll leave it up to you

[mariacm12]

I agree, I made a new issue for those two errors in #103. I think you should merge this one for now.

[ijpulidos]

Just for future reference, this needed to update the pins on the gufe requirements, since now we are depending on gufe 1.6.0 after this change. I'll be taking care of that in #106