[docs/deployment/docker-swarm] precision about ipv6

[arthurzenika]

Description

Improve the doc about docker-swarm deployment

Motivation and Context

• I have raised an issue to propose this change (required)

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have signed-off my commits with git commit -s

[derek]

Thank you for your contribution. I've just checked and your commit doesn't appear to be signed-off. That's something we need before your Pull Request can be merged. Please see our contributing guide.
Tip: if you only have one commit so far then run: git commit --amend --signoff and then git push --force.

[derek]

Thank you for your interest in this project, but unfortunately your commit did not follow the contributing guidelines.

Check the following:

• Did you add a "Signed-off-by" line to the commit?
• Did you send a PR to fix a typo instead of raising an issue?
• Are you a first-time contributor who has skipped reading the contributing guidelines?

See also Hacktoberfest quality standards

[arthurzenika]

Related to #242

[arthurzenika]

@derek Can you tell me how to re-open this pull request ? Can I suggest a shorter CONTRIBUTING document for docs ?