GPU usage in docs

https://github.com/InseeFrLab/torchTextClassifiers/blame/9a8b215dde66d6d549f4e479899edbb7c287fc12/docs/source/getting_started/quickstart.md#L262

`accelerator="gpu"` does not work for me, but `accelerator="cuda" ` works instead (as in `torch.device`).

Details of the error:

```
Traceback (most recent call last):
File "path/to/train_script.py", line xxx, in main
ttc.train(
~~~~~~~~~^
X_train,
^^^^^^^^
...<4 lines>...
verbose=True,
^^^^^^^^^^^^^
)
^
File path/to/torchTextClassifiers/torchTextClassifiers.py", line 401, in train
device = torch.device(training_config.accelerator)
RuntimeError: Expected one of cpu, cuda, ipu, xpu, mkldnn, opengl, opencl, ideep, hip, ve, fpga, maia, xla, lazy, vulkan, mps, meta, hpu, mtia, privateuseone device type at start of device string: gpu
```

Open docs/source/getting_started/quickstart.md at the referenced line and compare the documented accelerator value with the accepted PyTorch device types shown in the traceback. Check torchTextClassifiers.py around line 401 and run the quickstart or its documentation checks; done means the quickstart uses a working accelerator value and no longer produces the reported device-string error.

Written by the indexing model from the issue text.