[Perf] Changing actor visibility should not compute actor matrix

[finetjul]

High-level description

vtkActor.onModified triggers a computeMatrix(). This is useless:

• when only the actor visibility is changed
• because there is already a mechanism that computes the matrix each time it is accessed

Steps to reproduce

call vtkActor.setVisibility() and see that computeMatrix() is recomputing the matrix.

Detailed Current Behavior

too slow

Environment

master