Suppress deprecation warning for CellSetSingleType::GetCellShape

The superclass method `CellSetExplicit::GetCellShape()` is marked
deprecated because it is a slow way to access the cell shape. However,
this deprecation is causing a warning with MSVC when implementing the
subclass `CellSetSingleType`'s override of that method (which is not
slow). Suppress this warning.
18 jobs for reverseconnection-precompiled
Status Name Job ID Coverage
  External
passed cdash-buildbot

passed vtk-m-dragnipur-osx-shared-debug+32bit_ids+64bit_coords+clang+tbb

passed vtk-m-dragnipur-osx-static-release+64bit_coords+clang+tbb

passed vtk-m-osheim-windows-shared-debug+ninja-vs-2017+tbb

passed vtk-m-osheim-windows-static-release+ninja-vs-2017+tbb

passed cdash-buildbot

passed vtk-m-dragnipur-osx-shared-debug+32bit_ids+64bit_coords+clang+tbb

passed vtk-m-dragnipur-osx-shared-debug+32bit_ids+64bit_coords+clang+tbb

00:12:23

passed vtk-m-dragnipur-osx-shared-debug+32bit_ids+64bit_coords+clang+tbb

00:12:17

passed vtk-m-dragnipur-osx-static-release+64bit_coords+clang+tbb

00:18:40

passed vtk-m-dragnipur-osx-static-release+64bit_coords+clang+tbb

00:18:42

passed vtk-m-dragnipur-osx-static-release+64bit_coords+clang+tbb

passed vtk-m-osheim-windows-shared-debug+ninja-vs-2017+tbb

00:25:30

passed vtk-m-osheim-windows-shared-debug+ninja-vs-2017+tbb

00:24:46

passed vtk-m-osheim-windows-shared-debug+ninja-vs-2017+tbb

passed vtk-m-osheim-windows-static-release+ninja-vs-2017+tbb

00:33:07

passed vtk-m-osheim-windows-static-release+ninja-vs-2017+tbb

00:33:16

passed vtk-m-osheim-windows-static-release+ninja-vs-2017+tbb