chore: fix slider indent (#13955)

packages/slider/src/main.vue

 <template>
-  <div class="el-slider"
+  <div
+    class="el-slider"
     :class="{ 'is-vertical': vertical, 'el-slider--with-input': showInput }"
     role="slider"
     :aria-valuemin="min"
@@ -21,7 +22,8 @@
       :debounce="debounce"
       :size="inputSize">
     </el-input-number>
-    <div class="el-slider__runway"
+    <div
+      class="el-slider__runway"
       :class="{ 'show-input': showInput, 'disabled': sliderDisabled }"
       :style="runwayStyle"
       @click="onSliderClick"