Fix pyvista deprecation warnings

[akaszynski]

There's an internal example we're working on that has these ugly warnings:

/home/alex/python/pyvista_venv3.8/lib/python3.8/site-packages/pyvista/core/dataset.py:1401: PyvistaDeprecationWarning: Use of `point_arrays` is deprecated. Use `point_data` instead.
  warnings.warn(
/home/alex/python/pyvista_venv3.8/lib/python3.8/site-packages/pyvista/core/dataset.py:1541: PyvistaDeprecationWarning: Use of `cell_arrays` is deprecated. Use `cell_data` instead.
  warnings.warn(

Please have this patched tomorrow for a release by the end of this week. Near trivial patch.

[RomanIlchenko1308]

thank you, Alex(@akaszynski),
I will try to finish it today!

[akaszynski]

Deprecation warnings fixed as of ansys-mapdl-reader==0.51.8. See log output from https://github.com/pyansys/pymapdl/runs/4820017708?check_suite_focus=true.

[da1910]

This looks like it's recurred - see pressure vessel example, amongst others

https://dev.mapdldocs.pyansys.com/examples/00-mapdl-examples/pressure_vessel.html