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GH-44570: [Release][R][Docs] Update `r/pkgdown/assets/versions.html` (#44572)

### Rationale for this change

It's still used at https://arrow.apache.org/docs/r/versions.html . So we should update it too.

### What changes are included in this PR?

Commit it.

### Are these changes tested?

Yes.

### Are there any user-facing changes?

No.
* GitHub Issue: #44570

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