Remove quotes around error in .eslintrc.js for consistency

Author: lydell

.eslintrc.js

@@ -34,7 +34,7 @@ module.exports = {
       },
     ],
     "no-self-compare": error,
-    "no-shadow": "error",
+    "no-shadow": error,
     "no-template-curly-in-string": error,
     "no-unmodified-loop-condition": error,
     "no-unneeded-ternary": warn,