GH-2972: Change output of .text to original string

[alanakbik]

Closes #2972

The .text property of the Sentence and Span object currently print a whitespace tokenized version of the string. This PR changes this so that .text will print the untokenized string instead.

# make example sentence
sentence = Sentence("George   Washington was here")
print(sentence)

# get a span from the sentence and print its text
entity = sentence.get_span(0, 2)
print(entity)
print(entity.text)

This now prints:

Sentence: "George   Washington was here"
Span[0:2]: "George   Washington"
George   Washington

Before, it printed:

Sentence: "George Washington was here"
Span[0:2]: "George Washington"
George Washington