doc: update pictures in documentation

### Describe the enhancement requested

At the moment pictures illustrate that vertex chunks are named `part0`, `part1`, etc., while they are actually named `chunk0`, `chunk1`, etc.

I'm afraid it may be confusing for users.

### Component(s)

Documentation

Locate the documentation page containing the attached illustration and compare its labels with the current vertex chunk naming. Update the picture so the illustrated chunks are named chunk0, chunk1, and so on instead of part0, part1, and verify that no outdated labels remain.

Written by the indexing model from the issue text.