Bug#1018954: comment on missing perl script

[Norwid Behrnd]

@Mathieu

As a tangential observation, running either

```bash
find / -name "vtk9" 2>/dev/null
locate --basename "vtk9"
find / -name "vtk" 2>/dev/null
locate --basename "vtk"
```

it is my impression the installation (in Debian 12/bookworm, testing) of
current libvtk9.1, libvtk9.1-qt, python3-vtk9, and vtk9 (all in version
9.1.0+really9.1.0+dfsg2-4) with synaptic doesn't provide a sub folder `vtk9`
at all.  There equally is the return of none with

```bash
find / -name "doc_header2doxygen.pl" 2>/dev/null
locate --basename "doc_header2doxygen.pl"
```

in line with your observation.  That Python does not mention a grave error

```bash
$ python
Python 3.10.6 (main, Aug 10 2022, 11:19:32) [GCC 12.1.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import vtk
>>> print(vtk.__version__)
9.1.0
>>> 
```

does not help in an other bug (1016549) either.