gh-71052: Enable test_concurrent_futures on platforms that support threading but not multiprocessing #104051

Job	Run time
Check for source changes	12s
Check if generated files are up to date	4m 50s
Address sanitizer	6m 34s
Ubuntu SSL tests with OpenSSL (1.1.1w)	1m 52s
Hypothesis tests on Ubuntu	4m 7s
Ubuntu SSL tests with OpenSSL (3.0.13)	2m 14s
Ubuntu SSL tests with OpenSSL (3.1.5)	1m 54s
Ubuntu SSL tests with OpenSSL (3.2.1)	2m 13s
CIFuzz	0s
Windows / build and test (x64)	13m 27s
Windows / build and test (x86)	13m 27s
Windows / build (arm64)	2m 49s
Windows (free-threading) / build and test (x64)	22m 3s
Windows (free-threading) / build (arm64)	2m 47s
Windows (free-threading) / build and test (x86)	23m 14s
macOS / build and test (macos-14)	7m 18s
macOS (free-threading) / build and test (macos-14)	7m 51s
macOS / build and test (macos-13)	8m 50s
Ubuntu / build and test	6m 14s
Ubuntu (free-threading) / build and test	7m 25s
macOS (free-threading) / build and test (macos-13)	12m 17s
Docs / Docs	1m 50s
Docs / Docs (Oldest Sphinx)	1m 40s
Docs / Doctest	5m 31s
All required checks pass	2s
	2h 40m 41s

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