[v4] Textarea: doesn't restore size after revert changes

[afbora]

To reproduce

1. Go to textarea field
2. Enter long long text
3. Revert page changes
4. See issue that textarea size still long (should be restore initial size)

Your setup

Kirby Version
Beta.3 (v4/develop)

[distantnative]

For this to be fixed, we need to add the .autosize() command back to the value watcher. To not have the event called twice, we should then remove the automatic set-up event listener from k-autosize