Col: fix the responsive bug caused by 'xs' variable (#13468)

packages/theme-chalk/src/common/var.scss

@@ -691,7 +691,7 @@ $--lg: 1200px !default;
 $--xl: 1920px !default;
 
 $--breakpoints: (
-  'xs' : (max-width: $--sm),
+  'xs' : (max-width: $--sm - 1),
   'sm' : (min-width: $--sm),
   'md' : (min-width: $--md),
   'lg' : (min-width: $--lg),