[CI] C++ extra jobs are executed with the `CI: Extra: R` label

[kou]

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

C++ extra jobs should be executed only with the CI: Extra and CI: Extra: C++ labels.

Example: #47994 has only the CI: Extra: R label but C++ extra jobs were executed: https://github.com/apache/arrow/actions/runs/22149812767/job/64037716629?pr=47994

Component(s)

Continuous Integration

[kou]

The CI: Extra: C++ label was added manually: #47994 (comment)

So this is not the current CI configuration problem.