Revert "fix(runner): bump undici to 8.5.0 with minimal lockfile delta"

This reverts commit 9132b29.

Author: jp-agenta

services/runner/package.json

@@ -34,7 +34,7 @@
     "acp-http-client": "0.4.2",
     "pi-acp": "0.0.29",
     "sandbox-agent": "0.4.2",
-    "undici": "8.5.0"
+    "undici": "8.3.0"
   },
   "devDependencies": {
     "@types/node": "^24.0.0",