VTK package: Correct netcdf-cxx dep (#36408)

VTK dropped netcdf-cxx as a dep in v8.2.0 (see
https://gitlab.kitware.com/vtk/vtk/-/merge_requests/4741).

Also use netcdf-cxx4 rather than netcdf-cxx (the latter is
deprecated and replaced by the former).

var/spack/repos/builtin/packages/vtk/package.py

@@ -154,7 +154,7 @@ class Vtk(CMakePackage):
     depends_on("lz4")
     depends_on("netcdf-c~mpi", when="~mpi")
     depends_on("netcdf-c+mpi", when="+mpi")
-    depends_on("netcdf-cxx")
+    depends_on("netcdf-cxx4", when="@:8.1.2")
     depends_on("libpng")
     depends_on("libtiff")
     depends_on("zlib-api")