Revert changes made in 93478375
Created by: Loisel
to FE CO2 emission factors that led to inconsistencies in the reporting, namely negative PE-to-SE emissions (the PE-to-SE emissions are calculated by substracting the FE emissions from a total given by IEA).
However, the emission factors should be revised at some point, since they are quite low compared to the IPCC values, see https://github.com/remindmodel/development_issues/issues/20