`image` column not automatically inferred if image dataset only contains 1 image
### Describe the bug

By default, the standard Image Dataset maps out `file_name` to `image` when loading an Image Dataset. 

However, if the dataset contains only 1 image, this does not take place 

### Steps to reproduce the bug

Input
(dataset with one image `multimodalart/repro_1_image`) 
```py
from datasets import load_dataset
dataset = load_dataset("multimodalart/repro_1_image")
dataset
```

Output: 
```py
DatasetDict({
    train: Dataset({
        features: ['file_name', 'prompt'],
        num_rows: 1
    })
})
```

Input 
(dataset with 2+ images `multimodalart/repro_2_image`) 
```py
from datasets import load_dataset
dataset = load_dataset("multimodalart/repro_2_image")
dataset
```

Output:
```py
DatasetDict({
    train: Dataset({
        features: ['image', 'prompt'],
        num_rows: 2
    })
})
```

### Expected behavior

Expected to map `file_name`  → `image` for all dataset sizes, including 1. 

### Environment info

Both latest main and 2.16.0