[BUG] display bug UnknownTokens

[Nadav Barak]

Describe the bug
Display looks weird when:

1. there are no unknown tokens
2. their percentage are very small
3. their percentage are very very small (rounded to 0 as in second image)

To Reproduce
run the check on just_dance_comment_analysis

from deepchecks.nlp.checks import UnknownTokens
from deepchecks.nlp.datasets.classification import just_dance_comment_analysis

train, _ = just_dance_comment_analysis.load_data(use_full_size=True)
UnknownTokens().run(train)

from deepchecks.nlp.checks import UnknownTokens
from deepchecks.nlp.datasets.classification import just_dance_comment_analysis

train, _ = just_dance_comment_analysis.load_data(use_full_size=False)
UnknownTokens().run(train)

[Noam Bressler]

Fixed