[ENH] relax dependency requirements on `times-fm` foundation model

Originally posted by @4x in #7138

I use Python 3.13 in Windows 11. Outside of sktime, I can use times-fm without any problem e.g. using something like

tfm = timesfm.TimesFm(
            hparams=timesfm.TimesFmHparams(
                backend=backend, per_core_batch_size=per_core_batch_size,
                horizon_len=horizon_len, num_layers=num_layers,
                use_positional_embedding=use_positional_embedding,
                context_len=context_len),
            checkpoint=timesfm.TimesFmCheckpoint(
                huggingface_repo_id="google/timesfm-2.0-500m-pytorch"
            )
        )

However, within sktime, the TimesFMForecaster requires (a) to downgrade to 3.10 and (b) to use... Linux:

ModuleNotFoundError
TimesFMForecaster requires an environment to satisfy packaging marker spec sys_platform == "linux", but environment does not satisfy it.

Could we kindly request to remove/relax these requirements? Sure, I can spin up a 3.10 venv but Linux?! Thank you