Thermoo for MC 1.21.9

• Updated to 1.21.9-rc1, this will likely work with the full release of 1.21.9. Per the LTS policy, this release represents the end of support for 1.21.6-8.
• While there are no breaking changes in Thermoo itself, changes to the Entity#getWorld() method in Minecraft means this release breaks binary compatibility with 1.21.6-8, so Thermoo is therefore getting a major version bump.
• Updated Argentine Spanish translations (thanks Texaliuz!)