Update test deps

Author: lukemelia

package.json

@@ -28,13 +28,13 @@
     "rsvp": "^3.5.0"
   },
   "devDependencies": {
-    "chai": "^3.5.0",
-    "chai-as-promised": "^6.0.0",
+    "chai": "^4.2.0",
+    "chai-as-promised": "^7.1.1",
     "ember-cli": "^3.18.0",
     "eslint": "^4.18.2",
     "github": "^0.2.4",
     "glob": "^7.1.1",
-    "mocha": "^3.2.0",
+    "mocha": "^7.1.2",
     "multiline": "^1.0.2",
     "release-it": "*"
   },