Fix inheritance of ambientocclusion property from parent model

[Uiniel]

I only noticed this bug because I encountered a similar bug (with a more noticeable property) in BlueMapModelLoaders.

A simple test with the following resource pack:

assets/minecraft/models/block/pink_wool.json :

{
  "parent": "minecraft:block/cube_all",
  "ambientocclusion": "false",
  "textures": {
    "all": "minecraft:block/pink_wool"
  }
}

assets/minecraft/models/block/white_wool.json :

{
  "parent": "minecraft:block/pink_wool",
  "textures": {
    "all": "minecraft:block/white_wool"
  }
}

assets/minecraft/models/block/light_gray_wool.json :

{
  "parent": "minecraft:block/pink_wool",
  "ambientocclusion": "true",
  "textures": {
    "all": "minecraft:block/light_gray_wool"
  }
}

Before:

After: