fossil fuel trade inconsistency

[russellhz]

This is a small issue, but caused some confusion. In the "Trade in GCAM" page, fossil fuel is still incorrectly labelled as Heckscher Ohlin: "Also, major energy commodities such as coal, gas, oil, bio-energy, etc. are also traded in a single world market with the Heckscher-Ohlin approach." https://jgcri.github.io/gcam-doc/details_trade.html#heckscher-ohlin

Whereas in the "Supply of Energy" page, it is listed as Armington: "GCAM models trade for coal, gas, oil, and bioenergy using an Armington approach that is described in fossil fuel trade." https://jgcri.github.io/gcam-doc/supply_energy.html#energy-trade