Update Electron

This pulls in a vulnerability fix. Fix isn't critical
(we appear unaffected), but it's good to do regardless

Author: pimterry

package-lock.json

@@ -38,7 +38,7 @@
     "@types/universal-analytics": "^0.4.2",
     "babel-plugin-transform-async-to-generator": "^6.24.1",
     "babel-preset-env": "^1.7.0",
-    "electron": "^4.0.0",
+    "electron": "^4.0.4",
     "electron-forge": "^5.2.3",
     "electron-prebuilt-compile": "4.0.0",
     "httptoolkit-server": "^0.1.5",