Fix code coverage WC version

[wjrosa]

Changes proposed in this Pull Request:

The minimum supported WooCommerce version that the Stripe extension now supports is 9.6. Because of it, the PHP code coverage GitHub action is falling, as the bootstrap is not loading the classes properly for this version (returning early in woocommerce_gateway_stripe_init).

Testing instructions

Code review. Check if the tests are still passing. Confirm the code review action executed on this branch successfully.

The fake methods introduced here to test the action will be removed before merging the PR.

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• Covered with tests (or have a good reason not to test in description ☝️)
• Tested on mobile (or does not apply)

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Post merge

• Added testing instructions to the Release Testing Instructions wiki page (or does not apply)
• Added the needs docs label (or does not apply)
• Included this PR in the Release Thread scope (or does not apply)

[github-actions]

📈 PHP Unit Code Coverage Report

Package	Line Rate	Health
includes/class-wc-stripe-mode.php	67%	➖
Summary	45% (7389 / 16360)	❌

[wjrosa]

Closing in favor of #4360