Fixing cython version

Signed-off-by: Umberto Zerbinati <zerbinati@maths.ox.ac.uk>

Author: Umberto Zerbinati

.github/workflows/release.yml

@@ -88,7 +88,7 @@ jobs:
 
       - name: Build and install PETSc
         run: |
-          pip install numpy setuptools
+          pip install numpy setuptools cython==3.0.12
           cd ..
           git clone --branch v3.23.0 https://gitlab.com/petsc/petsc.git
           cd petsc