Update hyperparameter_search.py
# What does this PR do?
1. PR #24384 results in many tests failing related to HP Search. https://huggingface.slack.com/archives/C02CH2YP4EQ/p1687823783572709
2. Error being `tests/deepspeed/test_deepspeed.py::TrainerIntegrationDeepSpeed::test_hyperparameter_search
(line 122)  TypeError: is_available() missing 1 required positional argument: 'self'` when `default_hp_search_backend` is called.
3. This PR fixes it.

Tested this via:
```
export CUDA_VISIBLE_DEVICES="0"
export RUN_SLOW="yes"
export LOGLEVEL=INFO

cd transformers

pytest -sv tests/deepspeed/test_deepspeed.py::TrainerIntegrationDeepSpeed::test_hyperparameter_search
```
_The documentation is not available anymore as the PR was closed or merged._