Previously we were only disabling the `input` handler when it was
triggered, which caused a race condition within the `keyup` handlers
which also was triggered by the `input` event. This fixes the issue by
also unbinding the `input` handlers within the `keyup` handler, to avoid
running into the race condition.
Thanks to @Eckankar for pointing out the race condition that still
existed in
66ae2ad1d5
This closes https://github.com/select2/select2/issues/3300
ca0fd7c195