Model chat: space out annotation buckets

[EricMichaelSmith]

Patch description

• For the model_chat crowdsourcing task, if the text of the annotation categories is very long, you can set the "show_line_breaks" field (see task_config/annotations_config.json) to true in order to put a line break between the checkbox and text string of each category. This was useful recently when we had a test with very long questions for each checkbox.

Testing steps
Test command:

python parlai/crowdsourcing/tasks/model_chat/run.py \
mephisto.architect.port=3005 \
mephisto.task.maximum_units_per_worker=1000000 \
mephisto.task.task_name=${TASK_NAME}

"show_line_breaks": false:

"show_line_breaks": true:

[meganung]

ah this is a great option that improves the UX nicely!