Feature/remove unnessary re for table ele in pdf

[JIAQIA]

RE_MULTISPACE_INCLUDING_NEWLINES is applied to all elements of the Text category after partitioning PDF files. The relevant code is shown below:

out_elements = []
for el in elements:
    if isinstance(el, PageBreak) and not include_page_breaks:
        continue

    if isinstance(el, Image):
        out_elements.append(cast(Element, el))
    # NOTE(crag): this is probably always a Text object, but check for the sake of typing
    elif isinstance(el, Text):
        el.text = re.sub(
            RE_MULTISPACE_INCLUDING_NEWLINES,
            " ",
            el.text or "",
        ).strip()
        if el.text or isinstance(el, PageBreak):
            out_elements.append(cast(Element, el))

Newlines will not be removed from Table or TableChunk elements now.

[JIAQIA]

This issue has a significant impact on our datasets because many of our image-based PDF files contain tabular data. Our OCR system extracts this information in Markdown format, where newline characters ("\n") are essential for preserving the table structure.