Other field character limit still shows when unchecked

[michellexliu]

Bug description
When the user fills in too many characters in the other field, then unchecks it and submits the form, the "You're over the character limit" still appears.

To Reproduce
Steps to reproduce the behavior:

1. Click on a checkbox other than "Other"
2. Click on other and fill the textbox until it's over the limit
3. Uncheck other
4. Click submit

Expected behavior
The error message about the Other character limit should not appear if the user has unchecked other.

Screenshots