Users were reporting offset issues when the retopology overlay
was disabled. The reason those issues were happening is because of
`vs_offset = min(vs_offset, vs_z * -0.5);`.
That line is necessary for proper functioning of the retopology
overlay, but causes issues at lower offset values (such as zero, when
the retopology overlay is disabled).
Fixes#109640
Pull Request: https://projects.blender.org/blender/blender/pulls/109657