Heroku: Pin yarn version to v1.22.17

We will rely on renovatebot to update the version for us if there are new releases

Author: Turbo87

package.json

@@ -139,7 +139,7 @@
   },
   "engines": {
     "node": "16.13.2",
-    "npm": "^8.0.0"
+    "yarn": "1.22.17"
   },
   "ember": {
     "edition": "octane"