vant-css: use hairline classes instead of mixins

packages/vant-css/src/cell.css

@@ -1,38 +1,23 @@
 @import './common/var.css';
-@import './mixins/border_retina.css';
-@import './icon.css';
 
 .van-cell {
   width: 100%;
   display: table;
-  position: relative;
   padding: 10px 15px 10px 0;
   box-sizing: border-box;
   line-height: 24px;
-  background-color: $c-white;
-  color: $c-black;
+  background-color: $white;
+  color: $text-color;
   font-size: 14px;
-  text-decoration: none;
   overflow: hidden;
 
-  &::after {
-    @mixin border-retina (bottom);
-  }
-
-  &:last-child {
-    &::after {
-      border-bottom: 0;
-    }
+  &:not(:last-child)::after {
+    border-bottom-width: 1px;
   }
 
   &-group {
     padding-left: 15px;
-    position: relative;
-    background-color: #fff;
-
-    &::after {
-      @mixin border-retina (top, bottom);
-    }
+    background-color: $white;
   }
 
   &__title {
@@ -47,7 +32,7 @@
     display: block;
     font-size: 12px;
     line-height: 1.2;
-    color: $c-gray-darker;
+    color: $gray-darker;
   }
 
   &__value {
@@ -73,12 +58,7 @@
       position: absolute;
       left: -7px;
       font-size: 14px;
-      color: #f44;
-    }
-
-    .van-cell__title {
-      float: none;
-      display: inline-block;
+      color: $red;
     }
   }
 
@@ -87,7 +67,7 @@
     top: 50%;
     right: 15px;
     transform: translateY(-50%);
-    color: $c-gray-dark;
+    color: $gray-dark;
     font-size: 12px;
   }
 }