Bump ember-source from 3.20.2 to 3.20.3

Bumps [ember-source](https://github.com/emberjs/ember.js) from 3.20.2 to 3.20.3.
- [Release notes](https://github.com/emberjs/ember.js/releases)
- [Changelog](https://github.com/emberjs/ember.js/blob/master/CHANGELOG.md)
- [Commits](emberjs/ember.js@v3.20.2...v3.20.3)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

package-lock.json

@@ -87,7 +87,7 @@
     "ember-qunit": "^4.6.0",
     "ember-resolver": "^8.0.0",
     "ember-router-scroll": "^2.0.2",
-    "ember-source": "~3.20.2",
+    "ember-source": "~3.20.3",
     "ember-svg-jar": "^2.2.3",
     "ember-template-lint": "^2.9.1",
     "ember-test-selectors": "^4.1.0",