[FIX] point_of_sale: blockui should be above the closing popup

The z index of the closing popup div was changed to a higher index than
the blockui z index. This commit sets the z index of the closing popup
to a lower value then the blockui z index.

task-3471040

closes odoo/odoo#132310

Signed-off-by: Joseph Caburnay (jcb) <jcb@odoo.com>

addons/point_of_sale/static/src/css/popups/popups.scss

@@ -17,7 +17,7 @@
     text-align:center;
     background-color: #fff;
     box-shadow: 0px 10px 20px rgba(0,0,0,0.4);
-    z-index:1200;
+    z-index:1060;
     border-radius: 4px;
 }