Update dependency ember-cli-htmlbars to v6

Author: renovate[bot]

ember/package.json

@@ -56,7 +56,7 @@
     "ember-cli-deploy-revision-data": "1.0.0",
     "ember-cli-deploy-sentry-cli": "2.3.0",
     "ember-cli-deploy-with-rsync": "0.3.0",
-    "ember-cli-htmlbars": "5.7.1",
+    "ember-cli-htmlbars": "6.3.0",
     "ember-cli-inject-live-reload": "2.0.2",
     "ember-cli-mirage": "2.1.0",
     "ember-cli-notifications": "6.3.4",