Grid Gizmo is visible through the Scene Game Objects when the Post Processing Layer is used on the Camera

How to reproduce:

1. Open the attached project ("Post Processing Grid Gizmo Issue.zip) and enter the "test" scene
2. Click on the Main Camera and add a "Post Process Layer" component to it
3. Observe the two cubes

Expected result: the grid gizmos are not visible through the cubes

Actual result: the grid gizmos are visible even though they're blocked from view by the cubes

Reproduced in: Post Processing 2.1.3; 2.1.0