HTML line breaks incorrectly preserved in Markdown output

### Bug

HTML line breaks are incorrectly preserved in the converted Markdown output, when they should be normalized to a single space. These line breaks are purely cosmetic in the HTML source and should not affect the rendered text.

#### Input document (`lorem.html`)

```html

Lorem Ipsum

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut
labore et dolore magna aliqua.

```

#### Actual output

```markdown
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut

labore et dolore magna aliqua.
```

#### Expected output

Line breaks within HTML paragraph tags should be treated as whitespace and converted to single spaces in Markdown output:

```markdown
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
```

### Steps to reproduce

```shell
$ docling lorem.html --to md
```

### Docling version

Docling version: 2.70.0
Docling Core version: 2.60.2
Docling IBM Models version: 3.11.0
Docling Parse version: 4.7.3
Python: cpython-314 (3.14.2)
Platform: Windows-11-10.0.26200-SP0

### Python version

Python 3.14.2