style: update

src/style/dark.scss

@@ -38,16 +38,12 @@ html.dark {
     .arrow-left,
     .arrow-right {
       box-shadow: none;
+      border-right: 1px solid $border-style;
     }
 
     .arrow-right {
       border-left: 1px solid $border-style;
     }
-
-    .arrow-left,
-    .arrow-right {
-      border-right: 1px solid $border-style;
-    }
   }
 
   /* vxe-table */