[FIX] point_of_sale: Receipt color after print

The color of the displayed receipt slightly changed after clicking on
"Print Receipt".

addons/point_of_sale/static/src/js/printers.js

@@ -47,9 +47,9 @@ var PrinterMixin = {
     htmlToImg: function (receipt) {
         var self = this;
         $('.pos-receipts').html(receipt);
-        $('.pos-receipt').addClass('pos-receipt-print');
+        $('.pos-receipts>.pos-receipt').addClass('pos-receipt-print');
         var promise = new Promise(function (resolve, reject) {
-            html2canvas($('.pos-receipt')[0], {
+            html2canvas($('.pos-receipt-print')[0], {
                 ignoreElements: function (node) {
                     // By default, html2canvas copies the whole DOM even if we just capture a part
                     // of it. When copying the list of products, it gets all of the product from the