Fix created_at/updated_at flaky comparison tests

[hectorgomezv]

Summary

This PR adds logic to manage the corner case where the update_at and created_at database fields have the same value after an insertion and update took place subsequently. Sometimes the operations are performed during the same millisecond so both timestamps are the same one, and the migration tests checking the updated_at is greater than created_at fail.

An example can be seen at https://github.com/safe-global/safe-client-gateway/actions/runs/11515722403/job/32056943212

Summary of all failing tests
FAIL migrations/deprecated/__tests__/00001_accounts.spec.ts
  ● Migration 00001_accounts › should add and update row timestamps

    expect(received).toBeGreaterThan(expected)

    Expected: > 1729849189006
    Received:   1729849189006

Changes

• Adds 1 millisecond delays to updated_at checks during the migrations tests.