shuf: Reduce malloc, perf +4%

[oech3]

mimalloc complained

[codspeed-hq]

Merging this PR will improve performance by 4.02%

⚡ 2 improved benchmarks
✅ 296 untouched benchmarks
⏩ 48 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Memory	shuf_repeat_sampling[50000]	1.2 MB	1.1 MB	+4.02%
⚡	Simulation	shuf_repeat_sampling[50000]	4.7 ms	4.5 ms	+4%

---

_{Comparing oech3:shuf-malloc (bb1ede3) with main (f0c71b2)²}

Footnotes

1. 48 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. ↩

2. No successful run was found on main (54cfd30) during the generation of this report, so f0c71b2 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/date/date-locale-hour (passes in this run but fails in the 'main' branch)
Note: The gnu test tests/expand/bounded-memory is now being skipped but was previously passing.
Congrats! The gnu test tests/pr/bounded-memory is now passing!