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

Author: renovate-bot

package-lock.json

@@ -53,7 +53,7 @@
     "@babel/register": "^7.0.0",
     "@istanbuljs/nyc-config-babel": "2.1.1",
     "axios": "0.19.0",
-    "babel-plugin-istanbul": "5.1.4",
+    "babel-plugin-istanbul": "6.0.0",
     "chai": "^4.1.2",
     "codecov.io": "0.1.6",
     "cz-conventional-changelog-default-export": "0.0.0-semantically-released.1",