Invalid value for publishTime.
I use this publishTime to determine retry timeouts, so I don't want this to break.

[REQUIRED] Environment info

firebase-tools:

13.13.2

Platform:

Mac OS 14.4

[REQUIRED] Test case

const example = onMessagePublished(
  {
    topic: 'example',
    timeoutSeconds: 540,
    memory: '2GiB',
    retry: true,
  },
 (event: CloudEvent<MessagePublishedData>) => {
    console.log(event.data.message.publishTime); //1970/01/01 00:00:00
  },
);

[REQUIRED] Steps to reproduce

Start the emulator with the following command and call pubsub.

firebase emulators:start

[REQUIRED] Expected behavior

The date and time will be the PUBLISHED date and time.
In addition, as a supplement, the current date and time are entered for 1gen.

[REQUIRED] Actual behavior

publishTime is 1970/01/01 00:00:00