Bump react from 16.6.0 to 16.6.3 (#2258)

Bumps [react](https://github.com/facebook/react) from 16.6.0 to 16.6.3.
- [Release notes](https://github.com/facebook/react/releases)
- [Changelog](https://github.com/facebook/react/blob/master/CHANGELOG.md)
- [Commits](facebook/react@v16.6.0...v16.6.3)

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

package.json

@@ -61,7 +61,7 @@
     "postcss": "^7.0.6",
     "postcss-cli": "^6.0.1",
     "prop-types": "^15.6.2",
-    "react": "16.6.0",
+    "react": "16.6.3",
     "react-dom": "16.6.1",
     "react-ga": "2.5.3",
     "shelljs": "^0.8.3",