Fix scene toolbar size and spacing.

[drocheam]

The decorated_scene toolbar has unnecessary additional vertical spacing that arises from the display of empty tool names. You can see this spacing for instance in the images in https://github.com/enthought/mayavi/issues/1348 .

This is due to the default value of show_tool_names being set to True in: https://github.com/enthought/pyface/blob/d6548833ee35e0d27b4db62316fbeef1a98497e5/pyface/action/i_tool_bar_manager.py#L32

This fix sets the value to False for the created ToolBarManager, therefore removing the spacing.