Update dependency babel-plugin-istanbul to v7

Author: renovate[bot]

package.json

@@ -31,7 +31,7 @@
     "@cypress/code-coverage": "1.14.0",
     "@cypress/webpack-preprocessor": "4.1.5",
     "babel-loader": "8.4.1",
-    "babel-plugin-istanbul": "5.2.0",
+    "babel-plugin-istanbul": "7.0.1",
     "cross-env": "5.2.1",
     "cypress": "3.8.3",
     "html-webpack-plugin": "3.2.0",