docs: Remove firewalld zone instructions

[polarathene]

Proposed changes

Remove instructions for migrating to the docker zone, which landed in moby releases since 2020H2.

A recent PR commit modified these docs for v23 to remove the 20.10.0 qualifier (which lost that context).

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Additional Context

This makes the current information confusing, and implies a user should run similar commands to get integration with firewalld.

• AFAIK, the feature review discussed a future improvement to support changing the zone, or assigning user-defined networks to custom zones, but this does not appear to have been pursued since.
• Removing docker0 from the docker zone, will reassign it back, or if assigned to another zone with --permanent cause a failure for dockerd starting due to a conflicting zone already assigned docker0.

Thus given the recent change, these instructions should be dropped, or additional context provided (note: third-party guides created in 2023 can be found advising to assign docker0 to trusted zone).

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[dvdksn]

@akerouanton can you PTAL? TIA!

[neersighted]

LGTM

[docker-robot]

Thanks for the pull request. We'd like to make our product docs better, but haven’t been able to review all the suggestions.
As our docs have also diverged, we do not have the bandwidth to review and rebase old pull requests.

If the updates are still relevant, review our contribution guidelines and rebase your pull request against the latest version of the docs, then mark it as fresh with a /remove-lifecycle stale comment.
If not, this pull request will be closed in 30 days. This helps our maintainers focus on the active pull requests.

Prevent pull requests from auto-closing with a /lifecycle frozen comment.

/lifecycle stale

[polarathene]

Since the PR was raised, the original file was deleted and the content for firewalls relocated.

Nothing has changed since the LGTM beyond adjusting to the new filename.

[polarathene]

@dvdksn @neersighted would it be possible to get this merged before it becomes stale again? 😅 Thanks :)

[neersighted]

I think we were waiting for @akerouanton to find time/bandwidth; so friendly poke 😀

[akerouanton]

LGTM