removed old command line scripts

[shimwell]

Description

This PR attempts to remove scripts which are less useful now the Python API has these capabilities

Alternative to #3297 which attempts to update and move the scripts.

I think these scripts are not tested in the CI and one of them raises error when run

This would also ease packaging, reduce maintenance, etc

openmc-ace-to-hdf5 - suggest users make use of IncidentNeutron.from_ace
openmc-plot-mesh-tally - breaks on AttributeError: module 'matplotlib' has no attribute 'use', suggest users make use of openmc-plotter
openmc-track-combine - suggest users make use of openmc.Tracks.combine
openmc-track-to-vtk - suggest users make use of openmc.Tracks.write_to_vtk
openmc-update-inputs - perhaps this one should be ported to the python API or can be left?
openmc-update-mgxs - the input this converts has been deprecated for a while now, do we still need this?
openmc-voxel-to-vtk suggest users make use of openmc.voxel_to_vtk

Fixes # (issue)

Checklist

• I have performed a self-review of my own code
• I have followed the style guidelines for Python source files (if applicable)