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GH-34301: [CI][Packaging][RPM][arm64] Use closer.lua to download KEYS (#34302)

### Rationale for this change

https://downloads.apache.org/ may not be stable on Travis CI.

### What changes are included in this PR?

Use https://www.apache.org/dyn/closer.lua to use suitable mirror.

### Are these changes tested?

Yes.

### Are there any user-facing changes?

No.
* Closes: #34301

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