cad/openvsp: update to 3.31.1

ChangeLog: https://github.com/OpenVSP/OpenVSP/releases/tag/OpenVSP_3.31.1

Features:

• Add ResetMeshDisplay button to StructScreen
• Structural assemblies can now be inserted with rest of vsp3 file.
• Measure probes and rulers can now be inserted with rest of vsp3 file.
• Drop Ubuntu 18.04 from automated build system.

VSPAERO Updates and Fixes:

• Adding sensitivities for reference quantities.
• Improve setting CpSteadyMin/Max in steady flow.
• Bump and synchronize versions to 6.4.5.

Bug Fixes:

• Improve Calculix handling of beam elements.
• Fix crash when writing *.vspgeom file from imported mesh.
• Fix Vinf activation with stability choice. Thanks Daniel R.
• Fix tags for CompGeom half*mesh. Fixes *.vspgeom half*mesh panel mode.
• Fix consistency of StructScreen current structure choice.
• Fix StructAssemblyScreen height for various recent changes.
• Fix writing of ghost nodes for half*geom *.vspgeom files.
• Fix ID handling for copy/paste and insert of structures. Thanks Bryan.
• Fix subsurface tagging bug with quad meshes.