Update dependency ember-power-select to v8

Author: renovate[bot]

ember/package.json

@@ -78,7 +78,7 @@
     "ember-maybe-import-regenerator": "0.1.6",
     "ember-modifier": "2.1.1",
     "ember-page-title": "6.2.1",
-    "ember-power-select": "4.1.4",
+    "ember-power-select": "8.7.0",
     "ember-qunit": "4.6.0",
     "ember-render-helpers": "0.2.0",
     "ember-resolver": "8.0.2",