[improvement] add slide-down class (#2134)

packages/actionsheet/index.vue

@@ -1,5 +1,5 @@
 <template>
-  <transition name="van-slide-bottom">
+  <transition name="van-slide-up">
     <div
       v-if="shouldRender"
       v-show="value"

packages/actionsheet/test/__snapshots__/index.spec.js.snap

@@ -1,7 +1,7 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
 exports[`callback events 1`] = `
-<div class="van-actionsheet" name="van-slide-bottom">
+<div class="van-actionsheet" name="van-slide-up">
   <ul class="van-hairline--bottom">
     <li class="van-actionsheet__item van-hairline--top"><span class="van-actionsheet__name">Option</span>
       <!---->