Bump @babel/plugin-proposal-class-properties from 7.3.4 to 7.4.0

Bumps [@babel/plugin-proposal-class-properties](https://github.com/babel/babel) from 7.3.4 to 7.4.0.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/master/CHANGELOG.md)
- [Commits](babel/babel@v7.3.4...v7.4.0)

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

package.json

@@ -50,7 +50,7 @@
   },
   "devDependencies": {
     "@babel/core": "^7.4.0",
-    "@babel/plugin-proposal-class-properties": "^7.3.4",
+    "@babel/plugin-proposal-class-properties": "^7.4.0",
     "@babel/plugin-syntax-dynamic-import": "^7.2.0",
     "@babel/preset-env": "^7.3.4",
     "babel-eslint": "^10.0.1",