Subtract emissions from natural gas for DAC from emiTeMkt

[katarkow]

Purpose of this PR

Discounting the emissions that are captured in the CDR module from using natural gas for DAC’s heat and used (e.g., for synfuels) within REMIND.

Type of change

(Make sure to delete from the Type-of-change list the items not relevant to your PR)

• [x] Bug fix
• [x] Minor change (default scenarios show only small differences)

Checklist:

• [ ] My code follows the coding etiquette
• [ ] I performed a self-review of my own code
• [ ] I explained my changes within the PR, particularly in hard-to-understand areas
• [ ] I checked that the in-code documentation is up-to-date
• [ ] I adjusted the reporting in remind2 where it was needed
• [ ] I adjusted forbiddenColumnNames in readCheckScenarioConfig.R in case the PR leads to deprecated switches
• [ ] All automated model tests pass (FAIL 0 in the output of make test)
• [ ] The changelog CHANGELOG.md has been updated correctly