Outdated import of ccx2paraview

https://github.com/precice/community-training/blob/bce21334bb1ba32371cf8de66617407ab3699bd3/fsi-workflow/02_solidSimulation/skeleton/convert2vtu.py#L2

Should be:

```
import ccx2paraview as ccx2p 
```

Probably changed in 3.2.0, but cannot find a related PR right now: https://github.com/calculix/ccx2paraview/releases/tag/v3.2.0