chore(dockerfile): bump alpine version to 3.15

[cyril-corbon]

Signed-off-by: Cyril Corbon corboncyril@gmail.com

Description
Bump alpine version to 3.15

Checklist

• Unit tests updated
• End user documentation updated

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[Raffo]

/lgtm
/approve

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This pull-request has been approved by: cyril-corbon, Raffo

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