[CI] Drop obsolete pkg-config@0.29.2 brew uninstall from cpp.yml and python.yml

[tadeja]

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

Perhaps brew uninstall pkg-config@0.29.2 || : workaround (from 2024 Nov commit c21d85d) can be removed also from /workflows/cpp.yml and python.yml (ruby.yml already changed), so the error message about "pkg-config@0.29.2" does not always show up in C++ and Python macOS CI logs.

Uninstalling /opt/homebrew/Cellar/pkgconf/2.5.1... (28 files, 534.1KB)
Error: No available formula with the name "pkg-config@0.29.2". Did you mean pkg-config-wrapper?

https://github.com/apache/arrow/actions/runs/26083383511/job/76690298042#step:4:50
https://github.com/apache/arrow/actions/runs/26083383511/job/76690298114#step:4:50
https://github.com/apache/arrow/actions/runs/25957828927/job/76307685754#step:4:39

Github actions runner arm64 macOS 15 got image update there in 2024: - pkg-config 0.29.2 + pkgconf 2.3.0 and currently on - pkgconf 2.5.1. Similarly pkgconf 2.5.1 for AMD64

Component(s)

Continuous Integration

[raulcd]

Issue resolved by pull request 49997
#49997