Release testing instructions for WC Payments 9.1.0

fix: Manual capture fails in the transaction detail screen with a customized order number

PR https://github.com/Automattic/woocommerce-payments/pull/10435

1. Install and activate a sequential order number plugin (like Sequential Order Numbers for WooCommerce or Sequential Order Numbers Pro for WooCommerce, which can be downloaded from here by any Automattic staff)
2. Create a new order with a payment that requires manual capture
3. Try to capture the payment from the transaction detail screen
4. Verify that the capture succeeds and no errors occur
5. Verify that order and subscription numbers are displayed correctly in the transactions list

Fix: Update Safe Mode notice to be consistent with new changes from Jetpack #10511

PR https://github.com/Automattic/woocommerce-payments/pull/10511

• Install this plugin https://jetpack.com/download-jetpack-beta/, then activate jetpack-debug-helper, then Identity Crisis Simulation Utility.
• Trigger between two types of notices, use this constant in wp-config.php, and change its value to either development or production: define( 'WP_ENVIRONMENT_TYPE', 'development' );
• Expect: see two different notices.
• Expect: in the two notices, all text contents and links are WooPayments-relevant.