[FIX] point_of_sale: modal correctly aligned in mobile

Every popup/modal was not correctly aligned in the mobile screen. It was never in the center and the right portion of the popup was never visible.
With this commit, all popups are now correctly placed in mobile.

closes odoo/odoo#72793

Signed-off-by: pimodoo <pimodoo@users.noreply.github.com>

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

@@ -38,6 +38,13 @@ div.modal.in {
     left: 50%;
 }
 
+@media screen and (max-width: 768px) {
+    .ui-dialog, .modal-dialog {
+        padding: 0;
+        overflow: auto;
+    }
+}
+
 /* --- Generic Restyling and Resets --- */
 
 html {