fix: `partition_pdf()` removes spaces from the text

[christinestraub]

Closes #2896.

This PR aims to fix partition_pdf() to keep spaces in text. The control character \t is now replaced with a space instead of being removed when merging inferred and embedded elements.

Testing

PDF: rok_20230930_1-1.pdf

elements = partition_pdf(
    filename="rok_20230930_1-1.pdf",
    strategy="hi_res",
)

print(str(elements[20]))

Results:

• PR

  Name of each exchange on which registered New York Stock Exchange

• main branch

  Nameofeachexchangeonwhichregistered NewYorkStockExchange