Update test bootstrap.php to resolve notice

[rawdreeg]

Changes proposed in this Pull Request:

Updates bootstrap.php to run install_woocommerce on the init hook to resolve the notice.

Closes #2669.

• [x] Do the changed files pass phpcs checks? Please remove phpcs:ignore comments in changed files and fix any issues, or delete if not practical.

Detailed test instructions:

1. Confirm tests pass without triggering a notice using the latest version of WooCommerce

Changelog entry

Tweak - Test environment setup to resolve notice