COMP: update VTK8 git tag
Including Clinck and Drag modification made in VTK: vtk/vtk!3160 (merged)
This is necessary for https://github.com/Slicer/Slicer/pull/770
GitLab update will be applied on June 28th, between 8am and 10:30am, EDT (UTC-04:00). This site may have intermittent delays during that time.
Including Clinck and Drag modification made in VTK: vtk/vtk!3160 (merged)
This is necessary for https://github.com/Slicer/Slicer/pull/770