Use the font scaling provided by vtkTextActor.

This will increase the size of fonts used on displays
with high pixel densities.

Change-Id: I5f35a691a4261128e6cac9a4f7135eb9540ffc9b
Bump VTK to get scalar bar changes.

Change-Id: I5148f41cc428f0912c639ee0827693645e1ad802
Merge topic 'scalar_bar_font_scale' into next

6aaf51f Bump VTK to get scalar bar changes.
4781104 Use the font scaling provided by vtkTextActor.