chore: remove unused js-yaml dependencies

These were added for slash-command YAML parsing but are no longer
needed since we removed slash-command preprocessing entirely

package.json

@@ -16,8 +16,6 @@
     "@octokit/graphql": "^8.2.2",
     "@octokit/rest": "^21.1.1",
     "@octokit/webhooks-types": "^7.6.1",
-    "@types/js-yaml": "^4.0.9",
-    "js-yaml": "^4.1.0",
     "node-fetch": "^3.3.2",
     "zod": "^3.24.4"
   },