feat: add scoped styles for audio element in MdPreview component

--bug=1058490 --user=刘瑞斌 【应用管理】查看应用对话日志-显示回复语音，部分按键被遮盖 https://www.tapd.cn/62980211/s/1731804

ui/src/components/markdown/MdPreview.vue

@@ -21,3 +21,10 @@ config({
   }
 })
 </script>
+
+<style lang="scss" scoped>
+:deep(audio) {
+  width: 300px;
+  height: 43px;
+}
+</style>