[minor] Missing indexes in account_changes

[telezhnaya]

Understood that I created the bug here

https://github.com/near/near-indexer-for-explorer/blob/master/src/db_adapters/account_changes.rs#L20

We enumerate, then we filter It's possible to have the indexes like <span class="error"><span class="error">[0, 1, 4, 6, 7]</span></span> It still gives the right sort order, but it may confuse the users