ci: updates for Rust 1.76

[davidhewitt]

Change Summary

Fixes new lint warnings from Rust 1.76.

Related issue number

N/A

Checklist

• Unit tests for the changes exist
• Documentation reflects the changes where applicable
• Pydantic tests pass with this pydantic-core (except for expected changes)
• My PR is ready to review, please add a comment including the phrase "please review" to assign reviewers

[codspeed-hq]

CodSpeed Performance Report

Merging #1191 will improve performances by 25.17%

_{Comparing dh/rust-1.76 (7a9e158) with main (44621f1)}

Summary

⚡ 4 improvements
✅ 142 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	dh/rust-1.76	Change
⚡	test_core_future_str	39.2 µs	32.3 µs	+21.26%
⚡	test_core_str	38.7 µs	31.9 µs	+21.47%
⚡	test_core_future	37.5 µs	30 µs	+25.17%
⚡	test_core_str	63.6 µs	56.5 µs	+12.6%

[sydney-runkle]

Amazing, thanks!