Update environment.yml (#531)

Author: pancetta

pySDC/projects/SDC_showdown/environment.yml

@@ -5,7 +5,7 @@ channels:
   - conda-forge
 dependencies:
   - mpich
-  - petsc4py
+  - petsc4py<3.22
   - matplotlib>=3.0
   - dill>=0.2.6
   - scipy>=0.17.1