raises_on_error = False should catch all exceptions, including HTTP errors

### Bug
A `requests.exceptions.HTTPError` raised when a PDF is retrieved from a remote URL with `DocumentConverter.convert_all()` is not caught when `raises_on_error` is set to `False`.

### Steps to reproduce
Run the following script with a link that returns a 404 response:
```
from docling.document_converter import DocumentConverter

source = ""
converter = DocumentConverter()
results = converter.convert_all([source])
for result in results:
print(result.document.export_to_markdown())
```

### Python version
```
Python 3.10.12
```