-Game view does not refresh on enabling/disabling "Storyboard Global Mute" option in Cinemachine Storyboard Component.
-It refreshes when the mouse is hovered on the Game View.

Steps to repro:
1. Create a new Project.
2. Windows > Package Manager > Cinemachine > Install.
3. Create a Virtual Camera from Cinemachine menu.
4. Add CinemachineStoryboard extension in the inspector.
5. Assign any texture to "Show Image" in the inspector.
6. Enable/Disable "Storyboard Global Mute" option.

Actual Result:
Game View does not refresh on enabling/disabling "Storyboard Global Mute" option.

Expected Result:
Game View should be refreshed on enabling/disabling "Storyboard Global Mute" option.

Tested in: 2020.1.0a21, 2019.3.0f6 (27ab2135bccf) with Package Version: 2.5.0, 2.4.0.

Note:
-"Storyboard Global Mute" feature introduced in Package version 2.4.0.
-Package version 2.4.0 is introduced in 2018.4.0f1.

Environment:
Occurring on Windows & Mac.