openfoam: ignore extended number of faces (fixes paraview#14235)

- occurs with foam-extend globalFaceZone, in which the faces list
  is longer than owner/neighbour lists (with the extra faces belonging
  to the globalFaceZone).

  Remedy by simply resetting the known NumFaces to be consistent with
  owner/neighbour information. The excess faces will simply be dragged
  along without being addressed. This is a minor memory overhead
  (versus truncating the face list), but only affects cases with
  globalFaceZone and still allows some possibility to handling in the
  future if desired.
  Adjustment consistent with CreateCellFaces() private method.