get_sentence_ngrams, get_neighbor_sentence_ngrams, same_sentence should be fonduer.utils.data_model_utils.textual?

[HiromuHota]

Description of the bug

get_sentence_ngrams, get_neighbor_sentence_ngrams, same_sentence are placed under fonduer.utils.data_model_utils.tabular module, but their names sound and their behaviours look textual.

To Reproduce

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Expected behavior

Move them into fonduer.utils.data_model_utils.textual?

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Environment (please complete the following information)

• Fonduer Version: 0.8.2

Additional context

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