glue datasets returning -1 for test split
### Describe the bug

Downloading any dataset from GLUE has -1 as class labels for test split. Train and validation have regular 0/1 class labels.  This is also present in the dataset card online. 

### Steps to reproduce the bug

```
dataset = load_dataset("glue", "sst2")
for d in dataset:
    # prints out -1
    print(d["label"]
```

### Expected behavior

Expected behavior should be 0/1 instead of -1. 

### Environment info

- `datasets` version: 2.4.0
- Platform: Linux-5.15.0-46-generic-x86_64-with-glibc2.17
- Python version: 3.8.16
- PyArrow version: 8.0.0
- Pandas version: 1.5.3


Hi @lithafnium, thanks for reporting.

Please note that you can use the "Community" tab in the corresponding dataset page to start any discussion: https://huggingface.co/datasets/glue/discussions

Indeed this issue was already raised there (https://huggingface.co/datasets/glue/discussions/5) and answered: https://huggingface.co/datasets/glue/discussions/5#63907885937867f0cb3cde31
> The test labels are not public.
>
> Note this dataset belongs to a benchmark: people send their predictions for the test split to GLUE (https://gluebenchmark.com/) and then they get a score in their leaderboard...
