[output spec] validator object field "value" should contain list

[mimir-d]

The validator reference value field has a primitive type currently (bool, numeric, string), but for some of the types (set in, not in) it should also be a list of primitives.

Change is trivial, in Validator object attributes:

    <tr>
        <td><em>value</em></td>
        <td>JSON: string, number, boolean</td>
        <td><strong>Yes</strong></td>
        <td>The value to use on the right side of the arithmetic comparison.</td>
    </tr>

to

    <tr>
        <td><em>value</em></td>
        <td>JSON: string, number, boolean, array</td>
        <td><strong>Yes</strong></td>
        <td>The value to use on the right side of the validation. If an array, it must be homogenous and contain supported primitive types.</td>
    </tr>