add missing CHANGELOG entry for 5973

[davidhewitt]

I should have added a CHANGELOG entry to #5973, I missed that it bumped the main Cargo.toml.

[codspeed-hq]

Merging this PR will improve performance by 13.8%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 1 improved benchmark
✅ 104 untouched benchmarks
⏩ 1 skipped benchmark¹

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
⚡	bench_pyclass_create	4.6 µs	4 µs	+13.8%

---

_{Comparing davidhewitt:hashbrown-changelog (89329d2) with main (cf4d883)}

Footnotes

1. 1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩