Bump cross-env from 5.2.1 to 6.0.3 (linuswillner#367)

Bumps [cross-env](https://github.com/kentcdodds/cross-env) from 5.2.1 to 6.0.3.
- [Release notes](https://github.com/kentcdodds/cross-env/releases)
- [Changelog](https://github.com/kentcdodds/cross-env/blob/master/CHANGELOG.md)
- [Commits](kentcdodds/cross-env@v5.2.1...v6.0.3)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Co-authored-by: null <27856297+dependabot-preview[bot]@users.noreply.github.com>

Author: dependabot-preview[bot]

package-lock.json

@@ -48,7 +48,7 @@
     "babel-loader": "^8.0.6",
     "babel-runtime": "^6.26.0",
     "codecov": "^3.6.1",
-    "cross-env": "^5.2.1",
+    "cross-env": "^6.0.3",
     "css-loader": "^3.2.0",
     "enzyme": "^3.10.0",
     "enzyme-adapter-react-16": "^1.15.1",