update styleguide

Author: mansona

package.json

@@ -102,7 +102,7 @@
     "ember-route-action-helper": "^2.0.5",
     "ember-sinon": "^4.1.1",
     "ember-source": "~3.28.8",
-    "ember-styleguide": "2.6.0-0",
+    "ember-styleguide": "^3.1.1",
     "ember-svg-jar": "^2.4.2",
     "ember-template-lint": "^3.15.0",
     "ember-test-selectors": "^6.0.0",