chore(deps): update alpine docker tag to v3.22.2

[renovate]

This PR contains the following updates:

Package	Update	Change
alpine	minor	3.21.3 -> 3.22.2

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[DavidePrincipi]

Upgrade to Alpine 3.22 is blocked by the version change of Dovecot, that is upgraded from 2.3 to 2.4.

The build of Dovecot's Flatcurve plugin fails and must be fixed.
BTW Flatcurve support for Dovecot 2.3 is EOL

https://slusarz.github.io/dovecot-fts-flatcurve/eol.html#fts-flatcurve-dovecot-ce-2-3-x-eol-end-of-life

[DavidePrincipi]

@copilot address the upgrade issues enduring automated tests do not fail

[Copilot]

@DavidePrincipi I've opened a new pull request, #206, to work on those changes. Once the pull request is ready, I'll request review from you.

[renovate]

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[DavidePrincipi]

Upgrade to 2.3 to 2.4 requires a configuration format change https://doc.dovecot.org/2.4.1/installation/upgrade/2.3-to-2.4.html