launch_mechanical has a version argument that is only supported if pypim is configured

[koubaa]

it should be usable without pypim.

Furthermore, pim should only be installed using a [pim] option.

pip install ansys-mechanical-core => pim not installed

pip install ansys-mechanical-core[pim] => pim installed

[koubaa]

There is still the open issue that the "version" argument of launch_mechanical doesn't do anything when not using PIM. Reopening