fix(test): explicitly added fileParallelism: false to ci

[MattHandzel]

Work around for #1666, explicitly make vitest test files in serial to prevent contamination of database.json. Ran ci pipeline with this change ~50 times and did not see any flakiness.

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[MikeMcC399]

@AtofStryker

• It would be good if the team could take a look at this PR relatively soon. We're continually experiencing occasional flake in workflows as described in Flaky unit tests #1666

[AtofStryker]

This seems like a reasonable suggestion, though we would be applying it globally and not just in CI. Let's give it a try!