fix: upgrade ember-source from 3.12.0 to 3.16.3

Snyk has created this PR to upgrade ember-source from 3.12.0 to 3.16.3.

See this package in NPM:
https://www.npmjs.com/package/ember-source

See this project in Snyk:
https://app.snyk.io/org/nodeshift-starters/project/255abb11-a6e1-48a1-87b7-513da98dce3a?utm_source=github&utm_medium=upgrade-pr

ember/client/package.json

@@ -39,7 +39,7 @@
     "ember-maybe-import-regenerator": "^0.1.6",
     "ember-qunit": "^4.4.1",
     "ember-resolver": "^7.0.0",
-    "ember-source": "~3.12.0",
+    "ember-source": "~3.16.3",
     "eslint-plugin-ember": "^6.2.0",
     "eslint-plugin-node": "^9.0.1",
     "loader.js": "^4.7.0",