Compatibility testing with Woo 8.8

[ankitguptaindia]

All Submissions:

• Have you written new tests for your changes, as applicable?
• Have you successfully run tests with your changes locally?
• Will this change require new documentation or changes to existing documentation?

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Changes proposed in this Pull Request:

• Bump WooCommerce "tested up to" version 8.8
• Bump WooCommerce minimum supported version to 8.6

Closes #213

Steps to test the changes in this Pull Request:

1. Run the e2e test using GitHub action to test this PR
2. All tests should be passed.
3. Manual Test - The plugin should give Notice when using an unsupported version of WooCommerce and WordPress.

Changelog entry

Dev - Bump WooCommerce "tested up to" version 8.8.
Dev - Bump WooCommerce minimum supported version to 8.6.

[dkotter]

Code here looks fine but E2E tests are failing which will need further investigation cc / @vikrampm1

[ankitguptaindia]

@iamdharmesh Could you please fix failed e2e cases? thanks!

[iamdharmesh]

@ankitguptaindia E2E tests are fixed. Failure was due to place order button label updates for the subscription. It's fixed now.

Thanks.