WooCommerce One Page Checkout 2.9.2

* Tweak: Reposition coupon field to after the product selection.
* Tweak: WC 3.9 compatibility.

* Tweak: Tooltip display in admin screen of category search.
* Tweak: WC 3.8 compatibility.

* New: Introduce helper to find if it's a frontend request
* New: Bumps WC tested up to version.
* Tweak: Updates notice copy to reflect minimum WC version
* Tweak: Update minimum required WC version
* Tweak: Removes WC 2.5 pre code
* Tweak: Remove duplicate jQuery selectors
* Fix: Hides shipping fields for virtual products
* Fix: Avoid duplicated notices when variables product is not selected
* Fix: Prevent errors while generating page via Gutenberg editor
* Fix: Removes use of deprecated jQuery function size()