WooCommerce Moneris Gateway 3.4.3

* Tweak - Allow Pay Page mode to be enabled in the plugin settings, rather than requiring a filter
* Misc - Add compatibility for WooCommerce High Performance Order Storage (HPOS)

* Fix - Ensure that credit card input field can be properly focused on iPad
* Fix - Replace deprecated `is_ajax()` function calls with `wp_doing_ajax()`
* Misc - Require WooCommerce 3.9.4 or greater

* Fix - Addressing the issue that prevent merchants from removing/deleting additional connection settings.
* Fix - Address intermittent issues affecting some merchants by updating Hosted Tokenization request