chore(deps): pin dependency jest to v23.6.0

package.json

@@ -96,7 +96,7 @@
     "google-libphonenumber": "3.2.18",
     "html-webpack-plugin": "3.2.0",
     "iso-3166-2": "0.4.0",
-    "jest": "^23.6.0",
+    "jest": "23.6.0",
     "jest-junit": "12.0.0",
     "keymirror": "0.1.1",
     "lodash.bindall": "4.4.0",