Bug 1854906 - Enable all ESLint rules on layout/tools/reftest. r=tnikkel

Depends on D189095

Differential Revision: https://phabricator.services.mozilla.com/D189096

.eslintrc.js

@@ -342,6 +342,7 @@ module.exports = {
     },
     {
       files: ["layout/**"],
+      excludedFiles: ["layout/tools/reftest/**"],
       rules: {
         "object-shorthand": "off",
         "mozilla/avoid-removeChild": "off",