Update Read the Docs build image to Ubuntu 24.04

[Copilot]

Ubuntu 20.04 LTS is being removed from Read the Docs on June 1, 2026. Projects still using it will fail to build after that date.

Changes

• .readthedocs.yaml: Bump build.os from ubuntu-20.04 to ubuntu-24.04

[Copilot]

Pull request overview

Updates the Read the Docs build environment to a supported OS image ahead of the Ubuntu 20.04 deprecation, ensuring documentation builds continue to succeed after Read the Docs removes 20.04.

Changes:

• Bump Read the Docs build.os from ubuntu-20.04 to ubuntu-24.04 in .readthedocs.yaml.

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💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[codspeed-hq]

Merging this PR will degrade performance by 13.91%

❌ 3 regressed benchmarks
✅ 9 untouched benchmarks
⏩ 2 skipped benchmarks¹

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	WallTime	test_run_lda[array_api]	4.3 ms	4.8 ms	-10.58%
❌	WallTime	test_run_lda[base]	2.5 ms	2.9 ms	-13.91%
❌	WallTime	test_jit[add]	813.9 ms	906.2 ms	-10.19%

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_{Comparing copilot/update-rtd-build-image (333e6a3) with main (8b6fe1e)}

Footnotes

1. 2 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩