Fix missing obsidian tile textures

'game:textures/block/stone/polishedrock/obsidian.png' not found (defined in Baked variant of block bricklayers:stonetile-normal-obsidian).
'game:textures/block/stone/polishedrock/obsidian-inside.png' not found (defined in Baked variant of block bricklayers:stonetile-normal-obsidian).