Fix CITATION.cff

Author: jochenklar

CITATION.cff

@@ -15,6 +15,6 @@ authors:
   given-names: Sauer
   orcid: https://orcid.org/0000-0002-9302-2131
 
-doi: https://doi.org/10.5281/zenodo.18937735
+doi: 10.5281/zenodo.18937735
 license: MIT
 repository-code: https://github.com/ISI-MIP/isimip-utils