Update dependency np to v6 (#305)

Author: renovate-bot

package.json

@@ -53,7 +53,7 @@
     "codecov": "3.6.4",
     "husky": "4.2.1",
     "lint-staged": "10.0.7",
-    "np": "5.2.1",
+    "np": "6.0.0",
     "npm-run-all": "4.1.5",
     "prettier": "1.19.1",
     "rimraf": "3.0.1",