fix dois

Author: MarleneBusch

joss_paper/paper.bib

@@ -134,7 +134,7 @@ @article{Sattler:2020
     pages = {110-132},
     year = {2020},
     issn = {0038-092X},
-    doi = {https://doi.org/10.1016/j.solener.2020.06.030},
+    doi = {doi.org/10.1016/j.solener.2020.06.030},
     author = {Johannes Christoph Sattler and Marc Röger and Peter Schwarzbözl and Reiner Buck and Ansgar Macke and Christian Raeder and Joachim Göttsche},
 }
 
@@ -147,7 +147,7 @@ @article{Ulmer:2011
     year = {2011},
     note = {SolarPACES 2009},
     issn = {0038-092X},
-    doi = {https://doi.org/10.1016/j.solener.2010.01.010},
+    doi = {doi.org/10.1016/j.solener.2010.01.010},
     author = {Steffen Ulmer and Tobias März and Christoph Prahl and Wolfgang Reinalter and Boris Belhomme},
 }