AdjustmentItemList::removeAdjustment isn't removing adjustment

here is the patch which gets our tests to pass when remvoving an adjustment.

PR: https://github.com/drupalcommerce/commerce/pull/493

Here's the deal. It might be my implementation. The `===` only works _if it is the exact same object_.

For example, the tests fail with `===` and creating a match object to try and remove.

    // Create new adjustment object, matching existing. Ensure it gets removed.
    $adjustment = new Adjustment([
      'type' => 'custom',
      'label' => '10% off',
      'amount' => new Price('-1.00', 'USD'),
    ]);
    $order->removeAdjustment($adjustment);
<code>

Whereas it passed in test when we have <code>$adjustments[0]

.

So I guess if we want to decide: you must retrieve the object, compare it, and choose to remove it. Or be able to reconstruct the adjustment and say "remove something like this".

You should get the adjustment, verify it, then remove it with the same object.