Fix decal modulate being passed as srgb instead of as linear color.

servers/rendering/renderer_rd/storage_rd/texture_storage.cpp

@@ -2965,7 +2965,7 @@ void TextureStorage::update_decal_buffer(const PagedArray<RID> &p_decals, const
 			dd.emission_rect[3] = 0;
 		}
 
-		Color modulate = decal->modulate;
+		Color modulate = decal->modulate.srgb_to_linear();
 		dd.modulate[0] = modulate.r;
 		dd.modulate[1] = modulate.g;
 		dd.modulate[2] = modulate.b;