GH-45356: [CI][R] Update MACOSX_DEPLOYMENT_TARGET to 11.6

[kou]

Rationale for this change

CRAN uses 11.6 as the minimal macOS version now:
https://cran.r-project.org/web/checks/check_flavors.html

What changes are included in this PR?

Update to 11.6 from 10.13.

Are these changes tested?

Yes.

Are there any user-facing changes?

No.

• GitHub Issue: [R] Can we bump MACOSX_DEPLOYMENT_TARGET from 10.13? #45356

[kou]

@github-actions crossbow submit r-binary-packages

[github-actions]

⚠️ GitHub issue #45356 has been automatically assigned in GitHub to PR creator.

[github-actions]

Revision: 5382335

Submitted crossbow builds: ursacomputing/crossbow @ actions-273f1a79dd

Task	Status
r-binary-packages

[raulcd]

👍 as per the issue description

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 4 benchmarking runs that have been run so far on merge-commit ca2f4d6.

There were 8 benchmark results with an error:

• Commit Run on test-mac-arm at 2025-01-28 21:49:49Z
  • tpch (R) with engine=arrow, format=native, language=R, memory_map=False, query_id=TPCH-03, scale_factor=1
  • tpch (R) with engine=arrow, format=parquet, language=R, memory_map=False, query_id=TPCH-03, scale_factor=1
• and 6 more (see the report linked below)

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 50 possible false positives for unstable benchmarks that are known to sometimes produce them.