Remove square brackets from getInputHTML

[mylesthedev]

It might pay to leave it up to the twig being passed through to have the square brackets.
It's much more difficult to remove [] in twig than it is to add them e.g. json_encode.

For example:

    {% set myArray = [] %}
    {% for item in items %}
        {% set myArray = myArray|merge([{
            'label': item.label,
            'value': item.id
        }]) %}
    {% endfor %}
    {{ myArray | json_encode() | raw }}