### Tested versions

- First reproducible in: v4.2.dev5.official [e3e2528ba]
- Reproducible in: v4.2.stable.official [46dc27791], v4.2.dev5.official [e3e2528ba], v4.2.dev6.official [57a6813bb]
- Not reproducible in: v4.1.3.stable.official [f06b6836a], v4.2.dev1.official [0c2144da9], v4.2.dev2.official [da81ca62a], v4.2.dev3.official [013e8e3af], v4.2.dev4.official [549fcce5f]

### System information

Godot v4.2.stable - Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 1080 (NVIDIA; 31.0.15.4617) - Intel(R) Core(TM) i5-8600K CPU @ 3.60GHz (6 Threads)

### Issue description

The `TileSet` `set_occlusion_layer_light_mask` method does not properly update the `TileSet`'s light mask, causing shadows to still be cast by the `TileSet` even when the light mask is changed using the method to a mask different from a given light source (or even an empty light mask). In v4.1.3.stable.official [f06b6836a] this method was working properly.

### Steps to reproduce

- Download and open the `MRPSetOcclusionLayerTileSet_4.2-stable` project folder using one of the reproducible Godot versions noted above.
- Run the project, and press the spacebar key. This will toggle the occlusion layer light mask value of the on-screen `TileMap`'s `TileSet` occlusion light mask between 0 and 1. You will see that the `TileMap` still casts shadows regardless of the new value of its `TileSets`'s occlusion layer light mask.

### Minimal reproduction project (MRP)

[MRPSetOcclusionLayerTileSetBug.zip](https://github.com/godotengine/godot/files/13592741/MRPSetOcclusionLayerTileSetBug.zip)

TileData *tile_data = atlas_source->get_tile_data(neighbor_cell.get_atlas_coords(), neighbor_cell.alternative_tile);
					if (tile_data && tile_data->get_terrain_set() == p_terrain_set) {
						neighbor_tile_data = tile_data;
					}
				}
			}
			int terrain = neighbor_tile_data ? neighbor_tile_data->get_terrain_peering_bit(TileSet::CellNeighbor(E_overlapping.value)) : -1;
			if (!p_ignore_empty_terrains || terrain >= 0) {
				if (!terrain_count.has(terrain)) {
					terrain_count[terrain] = 0;
				}
				terrain_count[terrain] += 1;
			}
		}
		
		int max = 0;
		int max_terrain = -1;
		for (const KeyValue<int, int> &E_terrain_count : terrain_count) {
			if (E_terrain_count.value > max) {
				max = E_terrain_count.value;
				max_terrain = E_terrain_count.key;
			}
		}
		
		if (max > 0) {
			TerrainConstraint c = E_constraint;
			c.set_terrain(max_terrain);
			constraints.insert(c);
		}
	}