[FIX] point_of_sale: no black backgrounded receipt

Like commit odoo/odoo@1c5c762f3c

On some device (like Android Mobile) where the background is printed,
the receipt (which is white) is surrounded by a black background.

This commit fixes it by matching the receipt background (cf. white)
for the whole document and avoiding to print unnecessary background colors.

opw-1940434

X-original-commit: cf1a555ca2bc474ead1ef4fc063e8210678800d9

addons/point_of_sale/static/src/css/pos.css

@@ -1696,6 +1696,9 @@ td {
 }
 
 @media print {
+    body {
+        background: white;
+    }
     body * {
         visibility: hidden;
     }