Always align on start on xs screen

e5446fb8d4ce reintroduced the rule but using text-center while it is justify-*
that is used for grid layout.

Closes #12807

sao/src/sao.less

@@ -1016,7 +1016,8 @@ input.column-boolean {
     }
 
     .xalign-center, .xalign-end {
-        text-align: start;
+        justify-self: start;
+        justify-content: start;
     }
 }