docs: streaming subscription example close #8552

[skovati]

Description

Update Postgres streaming subscription example to be both valid and sound. I updated the batch size comment to 2 instead of the batch_size in the subscription itself, since the example shows 2 rows coming back.

There was another PR opened for this issue in a fork, but since that PR was closed the change didn't make it upstream, so I opened this PR. This PR also follows the new documentation structure.

Changelog

• [X] CHANGELOG.md is updated with user-facing content relevant to this PR. If no changelog is required, then add the no-changelog-required label.

Affected components

• [x] Docs

Related Issues

#8552

[hasura-bot]

Beep boop! :robot:

Hey @skovati, thanks for your PR!

One of my human friends will review this PR and get back to you as soon as possible.

Stay awesome! :sunglasses:

[CLAassistant]

All committers have signed the CLA.

[praveenweb]

This closes https://github.com/hasura/graphql-engine/issues/8552

[hasura-bot]

Beep boop! :robot:

Awesome work @skovati!

Your changes were merged successfully. All of us at Hasura :heart: what you did.

Thanks again :hugs: