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GH-37334: [Packaging][Release][RPM] Don't remove old repodata/* (#37351)

### Rationale for this change

If we remove them, users can't use Yum repositories for unsupported distributions such as Amazon Linux 2.

### What changes are included in this PR?

This keeps garbage in repodata/* but we can accept it because we'll migrate to Debian/RPM type repositories eventually. We don't manage repodata/* by ourselves after we migrate to Debian/RPM type repositories.

See also: GH-37350

### Are these changes tested?

No. I hope that this works.

### Are there any user-facing changes?

Yes.
* Closes: #37334

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