improve the way of applying the style class

Author: timur27

client/checkout/express-checkout-buttons.scss

@@ -27,6 +27,10 @@
 		#wcpay-express-checkout-element {
 			opacity: 1;
 		}
+
+		#wcpay-express-checkout-button-separator {
+			opacity: 1;
+		}
 	}
 
 	// WooPay button is always visible

client/express-checkout/button-ui.js

@@ -42,10 +42,9 @@ const expressCheckoutButtonUi = {
 	},
 
 	showContainer: () => {
-		const $container = jQuery( expressCheckoutElementId ).closest(
-			'.wcpay-express-checkout-wrapper'
-		);
-		$container.addClass( 'is-ready' );
+		get$Container()
+			.closest( '.wcpay-express-checkout-wrapper' )
+			.addClass( 'is-ready' );
 	},
 };