Update dependency ember-source to v3.21.1

Author: renovate-bot

package-lock.json

@@ -88,7 +88,7 @@
     "ember-qunit": "4.6.0",
     "ember-resolver": "8.0.2",
     "ember-router-scroll": "2.0.2",
-    "ember-source": "3.20.3",
+    "ember-source": "3.21.1",
     "ember-svg-jar": "2.2.3",
     "ember-template-lint": "2.11.0",
     "ember-test-selectors": "4.1.0",