Update Pub/Sub Emulator

MEDIUM W012: Unverifiable external dependency detected (runtime URL that controls agent).

• Potentially malicious external URL detected (high risk: 0.90). The skill instructs uploading and setting pubsub.remoteUrl to the Firebase storage location (gs://firebase-preview-drop/emulator/), which the emulator will download at runtime and execute as a binary, so this is a required remote dependency that can execute remote code.