Update carbon-management.yaml

[jayfuhrman]

re: issue #265 I suggest adding a new tier1 variable to reflect fossil or biomass carbon e.g., in plastics or asphalt manufacture that is embedded in the product, rather than being emitted. In my view only biomass-derived carbon should be reported as carbon removal. @fschreyer

[danielhuppmann]

This proposed variable seems to be a duplicate of "Carbon Capture|Utilization|Materials|*".

And "Carbon Removal|*" describes "Gross removals of carbon dioxide (CO2) from atmospheric origin or biomass through deliberate human activities" (see the description).