FIX fix merge-up

[GuySartorelli]

Fixes a bad merge-up

I forgot to apply these changes before committing this merge-up.

This PR:

1. fixes the format of the provideSortFieldBecomesIndexes() data provider - it may not actually pass the test, but the format is correct. Fixing the test if it is failing will be a separate follow-up PR. Fixing tests is not part of the merge-up, but updating the style of the provider to match the other scenarios is.
2. Removes array_keys call to match the other call to DataObjectSchema::deriveIndexFromSort()

Issue

• Index on default_sort doesn't take field type into account #11778

[emteknetnz]

Code is fine

CI broken

[GuySartorelli]

From the PR description

it may not actually pass the test, but the format is correct. Fixing the test if it is failing will be a separate follow-up PR. Fixing tests is not part of the merge-up, but updating the style of the provider to match the other scenarios is.