Remove unused set fe_tax_sub36

[ricardarosemann]

Purpose of this PR

Remove the set fe_tax_sub36 from the buildings module as it is no longer used: All entries in this set are written to fe_tax_sub_sbi. But this set is only called with fe_tax_sub_sbi("fehos", <input>) whereas fe_tax_sub36 contains no elements with "fehos" as the first entry.

Moreover, no other set elements are ever added to fe_tax_sub_sbi, meaning that fe_tax_sub_sbi("fehos", <input>) is empty. This issue should be addressed separately by cleaning up the 11_aerosols module, where fe_tax_sub_sbi is called, and will not directly be addressed in this PR. @laurinks @gunnar-pik

Type of change

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Parts concerned

• ☑️ GAMS Code
• ◻️ R-scripts
• ◻️ Documentation (GAMS incode documentation, comments, tutorials)
• ◻️ Input data / CES parameters
• ◻️ Tests, CI/CD (continuous integration/deployment)
• ◻️ Configuration (switches in main.gms, default.cfg, and scenario_config*.csv files)
• ◻️ Other (please give a description)

Impact

• ◻️ Bug fix
• ☑️ Refactoring
• ◻️ New feature
• ◻️ Change of parameter values or input data (including CES parameters)
• ◻️ Minor change (default scenarios show only small differences)
• ◻️ Fundamental change of results of default scenarios

Checklist

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In the end all checkboxes must be ticked before you can merge.

• I executed the automated model tests (make test) after my final commit and all tests pass (FAIL 0)
• I adjusted the reporting in remind2 if and where it was needed
• I adjusted the madrat packages (mrremind and other packages involved) for input data generation if and where it was needed
• My code follows the coding etiquette
• 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 forbiddenColumnNames in readCheckScenarioConfig.R in case the PR leads to deprecated switches
• I updated the CHANGELOG.md correctly (added, changed, fixed, removed, input data/calibration)

Further information (optional)

• Runs with these changes are here: Could not yet be done due to the cluster down time. I will also specifically check that this PR has no effect on related parameters.
• Comparison of results (what changes by this PR?):