[fix][doc] Update description about the initialization of cluster metadata

[momo-jun]

Motivation

Fix the doc issue #12488.
The initial doc PR #12567 didn't fix the issue properly due to the incorrect file directory.

Modifications

1. Update the description about the initialization of cluster metadata (content inherited from initial doc PR).
2. Remove the incorrect object "for each cluster in your instance" because it is a deployment topic for a single Pulsar cluster.

Note that the same changes will be applied to more versioned docs since 2.7.2 as soon as the PR gets approval.

Documentation

• doc

[momo-jun]

@codelipenghui @Anonymitaet can you please review this doc PR? Thanks.

[github-actions]

@momo-jun:Thanks for your contribution. For this PR, do we need to update docs?
(The PR template contains info about doc, which helps others know more about the changes. Can you provide doc-related info in this and future PR descriptions? Thanks)

[github-actions]

@momo-jun:Thanks for providing doc info!

[Anonymitaet]

is this the correct file? or is this (https://github.com/apache/pulsar/blob/master/site2/website/versioned_docs/version-2.7.3/deploy-bare-metal.md) the correct one?

[momo-jun]

is this the correct file? or is this (https://github.com/apache/pulsar/blob/master/site2/website/versioned_docs/version-2.7.3/deploy-bare-metal.md) the correct one?

I think it is a common issue that should be fixed in multiple versions. So I started with the latest one.