Fixes the following error as seen in
https://github.com/Automattic/woocommerce-payments/actions/runs/13581864590/job/37969236625

1) WC_Payments_Incentives_Service_Test::test_get_connect_incentive_has_orders_is_cached_longer_when_has_orders
Failed asserting that 5183999 is identical to 5184000.

/home/runner/work/woocommerce-payments/woocommerce-payments/tests/unit/test-class-wc-payments-incentives-service.php:409
/tmp/wordpress/wp-includes/class-wp-hook.php:326
/tmp/wordpress/wp-includes/plugin.php:205
/tmp/wordpress/wp-includes/option.php:1517
/home/runner/work/woocommerce-payments/woocommerce-payments/includes/class-wc-payments-incentives-service.php:480
/home/runner/work/woocommerce-payments/woocommerce-payments/includes/class-wc-payments-incentives-service.php:262
/home/runner/work/woocommerce-payments/woocommerce-payments/includes/class-wc-payments-incentives-service.php:203
/home/runner/work/woocommerce-payments/woocommerce-payments/tests/unit/test-class-wc-payments-incentives-service.php:418
phpvfscomposer:///home/runner/work/woocommerce-payments/woocommerce-payments/vendor/phpunit/phpunit/phpunit:97

Changes proposed in this Pull Request

This PR fixes the flaky test test_get_connect_incentive_has_orders_is_cached_longer_when_has_orders in WC_Payments_Incentives_Service_Test that was failing intermittently due to timing precision issues. The test was asserting an exact match for cache expiration time (60 days in seconds), but due to the nature of PHP's time() function and the slight delays between calculations, this could occasionally fail.

The change modifies the test assertion to allow for a small tolerance (≤ 5 seconds) in the expiration time check, making the test more resilient while still maintaining its effectiveness in catching real issues.

There is an alternative approach by mocking time functions like in the server repo but I don't want to make it complicated, and this is still good to address the root cause.

Testing instructions

• Just run tests for this class WC_Payments_Incentives_Service_Test and confirm there is no issue.

• Run npm run changelog to add a changelog file, choose patch to leave it empty if the change is not significant. You can add multiple changelog files in one PR by running this command a few times.
• Covered with tests (or have a good reason not to test in description ☝️)
• Tested on mobile (or does not apply)

Post merge

• No need - Link to testing instructions from release testing doc following these instructions : Add link here / 'QA Testing Not Applicable'
• No need - Add or update critical flows and testing instructions for critical flows, if applicable.
• No need - Add what's changed (description, screenshot, demo videos etc.) to the release announcement post, if applicable.