Meshes with dynamic GI mode have wrong lighting with lightmaps and Physical Light Units enabled

### Tested versions

v4.2.1.stable.official [b09f793f5]

### System information

Godot v4.2.1.stable - Windows 10.0.22621 - Vulkan (Forward+) - dedicated AMD Radeon RX 6700 XT (Advanced Micro Devices, Inc.; 31.0.23013.1023) - AMD Ryzen 7 5700X 8-Core Processor (16 Threads)

### Issue description

Dynamic meshes do not properly receive lighting fromn lightmaps when PLU is enabled, resulting in very dark indirect lighting:


### Steps to reproduce

1. Set up a scene with lightmaps and PLU enabled
2. Add a mesh and set its GI mode to dynamic

### Minimal reproduction project (MRP)

[Lightmap.zip](https://github.com/godotengine/godot/files/14048990/Lightmap.zip)

Open the linked Lightmap.zip minimal reproduction project and follow the listed steps with lightmaps and Physical Light Units enabled. Compare the lighting of a mesh using dynamic GI mode with the expected indirect lighting; the issue is complete when dynamic meshes receive correct lightmap lighting under PLU.

Written by the indexing model from the issue text.