Bump ember-source from 6.7.0 to 6.8.0 (#915)

Bumps [ember-source](https://github.com/emberjs/ember.js) from 6.7.0 to 6.8.0.
- [Release notes](https://github.com/emberjs/ember.js/releases)
- [Changelog](https://github.com/emberjs/ember.js/blob/main/CHANGELOG.md)
- [Commits](https://github.com/emberjs/ember.js/commits)

---
updated-dependencies:
- dependency-name: ember-source
  dependency-version: 6.8.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

package.json

@@ -55,7 +55,7 @@
     "ember-page-title": "^9.0.1",
     "ember-qunit": "^8.0.1",
     "ember-resolver": "^13.0.0",
-    "ember-source": "~6.7.0",
+    "ember-source": "~6.8.0",
     "ember-source-channel-url": "^3.0.0",
     "ember-template-lint": "^7.0.0",
     "ember-try": "^4.0.0",