[C++] arrow-compute.pc is installed twice

[kou]

Describe the bug, including details regarding any error messages, version, and platform.

For example:

https://github.com/apache/arrow/actions/runs/16861402303/job/47762113061#step:7:2329

-- Installing: /opt/conda/envs/arrow/lib/pkgconfig/arrow-compute.pc

https://github.com/apache/arrow/actions/runs/16861402303/job/47762113061#step:7:2449

-- Up-to-date: /opt/conda/envs/arrow/lib/pkgconfig/arrow-compute.pc

Component(s)

C++

[kou]

Issue resolved by pull request 47304
#47304