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GH-45166: [CI][C++] Upgrade Alpine Linux to 3.18 from 3.16 (#45168)

### Rationale for this change

Alpine Linux 3.16 reached EOL.

### What changes are included in this PR?

Use Alpine Linux 3.18 that is the oldest maintained version.

### Are these changes tested?

Yes.

### Are there any user-facing changes?

No.
* GitHub Issue: #45166

Authored-by: Sutou Kouhei <kou@clear-code.com>
Signed-off-by: Jacob Wujciak-Jens <jacob@wujciak.de>