do not define steel CCS MAC curve for pbs steel and cm_optimisticMAC

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

Purpose of this PR

Type of change

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

• [ ] Bug fix
• [ ] Refactoring
• [ ] New feature
• [ ] Minor change (default scenarios show only small differences)
• [ ] Fundamental change
• [ ] This change requires a documentation update

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

Further information (optional):

• Test runs are here:
• Comparison of results (what changes by this PR?):