Make `Version` hashable
_The documentation is not available anymore as the PR was closed or merged._
Add `__hash__` to the `Version` class to make it hashable (and remove the unneeded methods), as  `Version("0.0.0")` is the default value of `BuilderConfig.version` and the default fields of a dataclass need to be hashable in Python 3.11.

Fix https://github.com/huggingface/datasets/issues/5230