GIProbe will still take into consideration material emission when disabled

[PanTrakX]

Godot version:
3.3.stable

OS/device including version:
I can provide if needed.

Issue description:
When baking GI Probe, it will bake the emission from materials even if its turned off but has a emission color set other than black.

Steps to reproduce:

1. Add a MeshInstance with a CubeMesh to the scene.
2. Add a material to the MeshInstance
3. Turn on emission and set a (bright) color like a cyan.
4. Turn off emission
5. Add a GI Probe
6. Bake GI Probe

Minimal reproduction project:
giprobe_bug.zip

[akien-mga]

Fixed by #48798.