fix 点击可搜索下拉框的箭头失效 bug

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当select组件带有filterable时，点击右侧小箭头需要点击两次方可显示下拉内容，所以在下拉内容隐藏时重置this.menuVisibleOnFocus为false可以解决

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[ziyoung]

非常感谢你的 pr。
在这个 pr中，我们把 select 的交互行为统一了。这个问题应该是已经解决的。https://deploy-preview-12210--element.netlify.com/#/zh-CN/component/select#ke-sou-suo