Revert "Upgrade typescript to 3.7.2 (#2237)"

[dleroux]

This reverts commit 9085064.
#2237

Microsoft has commited a breaking change in a minor release of typescript
microsoft/TypeScript#33939

WHY are these changes introduced?

Fixes #0000

WHAT is this pull request doing?

How to 🎩

🖥 Local development instructions
🗒 General tophatting guidelines
📄 Changelog guidelines

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

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

export function Playground() {
  return (
    <Page title="Playground">
      {/* Add the code you want to test in here */}
    </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

[github-actions]

💦 Potential splash zone of changes introduced to src/**/*.tsx in this pull request:

Files modified	9
Files potentially affected	1

Details

All files potentially affected (total: 1)

• /src/components/AppProvider/AppProvider.tsx

📄 package.json (total: 0)

Files potentially affected (total: 0)

🧩 src/components/ContextualSaveBar/ContextualSaveBar.tsx (total: 0)

Files potentially affected (total: 0)

🧩 src/components/DropZone/tests/DropZone.test.tsx (total: 0)

Files potentially affected (total: 0)

🧩 src/components/RangeSlider/RangeSlider.tsx (total: 0)

Files potentially affected (total: 0)

🧩 src/components/RangeSlider/components/DualThumb/tests/DualThumb.test.tsx (total: 0)

Files potentially affected (total: 0)

🧩 src/components/ThemeProvider/ThemeProvider.tsx (total: 1)

Files potentially affected (total: 1)

• /src/components/AppProvider/AppProvider.tsx

🧩 src/components/Toast/Toast.tsx (total: 0)

Files potentially affected (total: 0)

🧩 src/utilities/tests/is-element-in-viewport.test.ts (total: 0)

Files potentially affected (total: 0)

📄 yarn.lock (total: 0)

Files potentially affected (total: 0)

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This comment automatically updates as changes are made to this pull request.
Feedback, troubleshooting: open an issue or reach out on Slack in #polaris-tooling.

[AndrewMusgrave]

✅