GH-50886: [C++][CI] Use bundled Abseil in macOS CI to avoid deprecation errors

[hiroyuki-sato]

Rationale for this change

google-cloud-cpp fails to build with Abseil 20260526.0 when deprecation warnings are treated as errors.

/Users/runner/work/arrow/arrow/build/cpp/_deps/google_cloud_cpp-src/google/cloud/stream_range.h:208:11: error: 'visit<UnpackVariant, std::variant<google::cloud::Status, google::cloud::storage::ObjectMetadata>>' is deprecated [-Werror,-Wdeprecated-declarations]
  208 |     absl::visit(UnpackVariant{*this}, std::move(v));
      |           ^

What changes are included in this PR?

Use bundled Abseil instead of Homebrew on macOS

Are these changes tested?

Yes.

Are there any user-facing changes?

No.

• GitHub Issue: [GLib][C++][CI] CI failure on ARM64 macOS GLib & Ruby #50886

[github-actions]

⚠️ GitHub issue #50886 has been automatically assigned in GitHub to PR creator.