Bump @babel/plugin-proposal-optional-chaining from 7.6.0 to 7.8.3

Bumps [@babel/plugin-proposal-optional-chaining](https://github.com/babel/babel) from 7.6.0 to 7.8.3.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/master/CHANGELOG.md)
- [Commits](babel/babel@v7.6.0...v7.8.3)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

package.json

@@ -31,7 +31,7 @@
     "@babel/cli": "^7.8.4",
     "@babel/core": "^7.8.3",
     "@babel/plugin-proposal-class-properties": "^7.8.3",
-    "@babel/plugin-proposal-optional-chaining": "^7.6.0",
+    "@babel/plugin-proposal-optional-chaining": "^7.8.3",
     "@babel/preset-env": "^7.8.3",
     "@babel/preset-react": "^7.0.0",
     "@babel/preset-typescript": "^7.3.3",