chore(deps): update dependency babel-plugin-istanbul to v6

Author: renovate-bot

package-lock.json

@@ -106,7 +106,7 @@
     "@babel/preset-env": "^7.4.4",
     "@babel/register": "^7.4.4",
     "babel-eslint": "^10.0.1",
-    "babel-plugin-istanbul": "^5.1.4",
+    "babel-plugin-istanbul": "^6.0.0",
     "chokidar-cli": "^2.0.0",
     "codecov": "^3.0.0",
     "cross-env": "^6.0.0",