修改Tabs组件翻页z-index为999(from 1000)

[focus0802]

重现条件：
1、使用Tabs组件；
2、使用Popup组件（向上）；
3、Popup弹出时暗色遮罩层z-index为999，Tabs翻页白色遮罩层z-index为1000。

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This change is 

[codecov]

Codecov Report

Merging #1512 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1512   +/-   ##
=======================================
  Coverage   66.13%   66.13%           
=======================================
  Files         226      226           
  Lines        2268     2268           
  Branches      696      696           
=======================================
  Hits         1500     1500           
  Misses        767      767           
  Partials        1        1

Flag	Coverage Δ
#rn	82.07% <ø> (ø)	⬆️
#web	65.35% <ø> (ø)	⬆️

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[cncolder]

@paranoidjk 有没有必要统一梳理一下 z-index

我看到有 999 1000 10000，都是随意加的数值。

[silentcloud]

目前 theme 里大部分都有，tab 的话是后期加多个滑动的时候漏掉了，这个可能需要加一个，跟设计师沟通一下 @paranoidjk

[paranoidjk]

@focus0802 我刚试了下，这里 z-index: 1000 是没有问题的，你遇到什么问题吗？能否提供可复现的demo或截图？

[focus0802]

@paranoidjk

[paranoidjk]

@focus0802 ok, get。我理解你的描述是把 tabs 放到 popup 里面，这样是没问题的。

[focus0802]

表达有误，不好意思！

[paranoidjk]

@focus0802 改成在这里添加 less 变量吧： https://github.com/ant-design/ant-design-mobile/blob/master/components/style/themes/default.less#L189

@tabs-pagination-zindex: 999;

[paranoidjk]

@focus0802 不用 close 的，继续在这个分支提交就好了

[paranoidjk]

最后merge的时候会 sqush and merge，合并你所有的 commit

[paranoidjk]

@focus0802 忘了说了，下次注意 commit message 尽量用英文 😄 ref #1528