in dublin-core extractor, update exception for GFZ

• update exceptions:
  • Data published at GFZ in years >= 2021 (PoF IV) can be mapped to "Earth and Environment"
    • explanation: in PoF I - PoF III (years < 2021), GFZ was funded within RFs Energy and E&E. Since PoF IV the only RF assigned to GFZ is E&E