[Tabs] Fix vertical alignment of Tabs DisclosureActivator

[rexmac]

WHY are these changes introduced?

Fixes #2086.

WHAT is this pull request doing?

Adds display: block style to Tabs .DisclosureActivator to match the styling of .Tab and fix the vertical alignment issue.

Before

After

How to 🎩

Copy-paste this code in playground/Playground.tsx:

import React from 'react';
import {Card, Page, Tabs} from '../src';

export function Playground() {
  const [selected, setSelected] = React.useState(0);
  const tabs = [
    {
      id: 'alpha',
      content: 'Alpha',
    },
    {
      id: 'bravo',
      content: 'Bravo',
    },
    {
      id: 'charlie',
      content: 'Charlie',
    },
    {
      id: 'delta',
      content: 'Delta',
    },
    {
      id: 'echo',
      content: 'Echo',
    },
    {
      id: 'foxtrot',
      content: 'Foxtrot',
    },
    {
      id: 'golf',
      content: 'Golf',
    },
    {
      id: 'hotel',
      content: 'Hotel',
    },
    {
      id: 'india',
      content: 'India',
    },
    {
      id: 'juliet',
      content: 'Juliet',
    },
    {
      id: 'kilo',
      content: 'Kilo',
    },
    {
      id: 'lima',
      content: 'Lima',
    },
    {
      id: 'mike',
      content: 'Mike',
    },
  ];

  return (
    <Page title="Playground">
      <Card>
        <Tabs
          tabs={tabs}
          selected={selected}
          onSelect={(selectedTabIndex) => setSelected(selectedTabIndex)}
        >
          <Card.Section title={tabs[selected].content}>
            <p>Tab {selected} selected</p>
          </Card.Section>
        </Tabs>
      </Card>
    </Page>
  );
}

🎩 checklist

• Tested on mobile
• Tested on multiple browsers
• Tested for accessibility
• Updated the component's README.md with documentation changes
• Tophatted documentation changes in the style guide
• For visual design changes, pinged one of @ HYPD, @ mirualves, @ sarahill, or @ ry5n to update the Polaris UI kit

[chloerice]

Tophat 👀 solid 👍

[ry5n]

Percy flags were either false positives, or show the Tabs issue being resolved. 👍

[AndrewMusgrave]

LGTM ✅

[BPScott]

Looks like you've got a bunch of extra fluff in your unreleased.md, can you remove that please - you probably branched just before we cut a release

[solutionwin2020]

Anyone tell me how to make polaris tabs vertical it is horizontal by default and i need this in vertical like in list on both desktop and mobile versions.

Thanks