Formatted the new styl code. (#1151)

Author: Jinjiang

themes/vue/source/css/_header.styl

@@ -44,16 +44,16 @@ body.docs
       border-bottom: none
     &.current
       &::after
-        content: ''
+        content: ""
         width: 0
         height: 0
         border-left: 5px solid $green
         border-top: 3px solid transparent
         border-bottom: 3px solid transparent
-        position: absolute;
-        top: 50%;
-        margin-top: -4px;
-        left: 8px;
+        position: absolute
+        top: 50%
+        margin-top: -4px
+        left: 8px
 
 .new-label
   position: absolute