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GH-45478: [CI][C++] Drop support for Ubuntu 20.04 (#45519)

### Rationale for this change

Ubuntu 20.04 will read EOL on 2025-05.

### What changes are included in this PR?

Remove jobs that use Ubuntu 20.04 or replace them with Ubuntu 22.04.

### Are these changes tested?

Yes.

### Are there any user-facing changes?

No.
* GitHub Issue: #45478

Authored-by: Sutou Kouhei <kou@clear-code.com>
Signed-off-by: Raúl Cumplido <raulcumplido@gmail.com>