Fix a typo

Author: Davknapp

src/Makefile.am

@@ -90,7 +90,7 @@ libt8_internal_headers = \
   src/t8_cmesh/t8_cmesh_offset.h \
   src/t8_vtk/t8_vtk_polydata.hxx \
   src/t8_vtk/t8_vtk_unstructured.hxx \
-  src/t8-vtk/t8_vtk_parallel.hxx \
+  src/t8_vtk/t8_vtk_parallel.hxx \
   src/t8_forest/t8_forest_cxx.h  \
   src/t8_forest/t8_forest_ghost.h \
   src/t8_forest/t8_forest_balance.h src/t8_forest/t8_forest_types.h \