_exchange_table_creation_ref missing renewables

[dt-woods]

I'm guessing these may get defined elsewhere (or that renewables are not found as exchange flows in the baseline), but just checking to make sure these commented out dictionaries in upstream_dict.py are supposed to be undefined in the long if-loop checking fuel types. I'd like to remove these undefined variables and I think a quick in-line comment would suffice for their removal. Let me know and I can add it.

https://github.com/USEPA/ElectricityLCI/blob/2232c41f2cb4fd333ad59c8710aa55906e6a7ed3/electricitylci/upstream_dict.py#L116

[m-jamieson]

I was going to say these seem like things I should've implemented in issues/150, but I forgot about them it seems. There's probably a thought here that implementing these commented flows would be the "right" answer, but I'm okay with something that just works right now. I say right answer because as of now, the way branch 150 works is to just add another input flow into the generation mixes that points to Construction - WIND - , resulting generation mixes with more than 100% input if that makes sense. FWIW, I'm okay leaving it as-is in favor of getting a new set of data out sooner.