Bump ember-cli from 3.15.1 to 3.18.0

Bumps [ember-cli](https://github.com/ember-cli/ember-cli) from 3.15.1 to 3.18.0.
- [Release notes](https://github.com/ember-cli/ember-cli/releases)
- [Changelog](https://github.com/ember-cli/ember-cli/blob/master/CHANGELOG.md)
- [Commits](ember-cli/ember-cli@v3.15.1...v3.18.0)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

package.json

@@ -18,7 +18,7 @@
     "broccoli-asset-rev": "^3.0.0",
     "chai": "^4.2.0",
     "ember-ajax": "^5.0.0",
-    "ember-cli": "~3.15.1",
+    "ember-cli": "~3.18.0",
     "ember-cli-dependency-checker": "^3.0.0",
     "ember-cli-eslint": "^5.1.0",
     "ember-cli-htmlbars": "^5.1.2",