chore(deps): pin dependency eslint to 6.4.0

Author: renovate-bot

package.json

@@ -69,7 +69,7 @@
     }
   },
   "devDependencies": {
-    "eslint": "^6.4.0",
+    "eslint": "6.4.0",
     "eslint-config-airbnb-base": "14.0.0",
     "eslint-plugin-import": "2.18.2",
     "jasmine-fix": "1.3.1"