Render xalign-end as start on small screen

As the rule was not in .form, it was not enough specific to apply.
Also on small screen we can keep centered the xalign-center

sao/src/sao.less

@@ -1150,11 +1150,11 @@ input.column-boolean {
         .form-container, .form-hcontainer, .form-vcontainer {
             display: block;
         }
-    }
 
-    .xalign-center, .xalign-end {
-        justify-self: start;
-        justify-content: start;
+        .xalign-end {
+            justify-self: start;
+            justify-content: start;
+        }
     }
 }