T7397: add "system kernel option quiet" to suppress boot messages (backport #1632)

[mergify]

Change Summary

Related Task(s)

• https://vyos.dev/T7397

Related PR(s)

• T7397: add "system kernel option quiet" to suppress boot messages vyos-1x#4477

Backport

• sagitta

Checklist:

• I have read the CONTRIBUTING document

  ---

  This is an automatic backport of pull request T7397: add "system kernel option quiet" to suppress boot messages #1632 done by Mergify.

[mergify]

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	both modified:   docs/configuration/system/option.rst

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