Revert "(Build-)Depends: tao-pegtl-dev to support external PEGTL (tao)"

Revert "(Build-)Depends: tao-pegtl-dev to support external PEGTL (tao)"

This reverts commit 40a6ef7735852b03253692722eeb812e3e8b6ef2.

tao-pegtl-dev 3.2.7 is not compatible with vtk 9.6.

There was MR !11999 to update VTK, but it has been abandoned,
and does not merge cleanly into current source.
https://gitlab.kitware.com/vtk/vtk/-/merge_requests/11999

See also
https://gitlab.kitware.com/vtk/vtk/-/work_items/17876
https://gitlab.kitware.com/vtk/vtk/-/work_items/18151

Cannot close Bug#1035426 until upstream sorts out their pegtl support.