GH-47704: [R] Update paths in nightly libarrow upload job (#47727)

### Rationale for this change

#45964 changed paths of pre-built Apache Arrow C++ binaries for R. But we forgot to update the nightly upload job.

### What changes are included in this PR?

Update paths in the nightly upload job.

### Are these changes tested?

No...

### Are there any user-facing changes?

Yes.
* GitHub Issue: #47704

Authored-by: Sutou Kouhei <[email protected]>
Signed-off-by: Nic Crane <[email protected]>

Author: kou