bump speedate to 0.15

[davidhewitt]

Change Summary

Among other fixes, this extends the range of supported timestamps all the way back to year 0.

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 #1526 will not alter performance

_{Comparing dh/speedate-0.15 (c3ea58a) with main (a1fa596)}

Summary

✅ 155 untouched benchmarks

[davidhewitt]

Integration test failure is expected; due to the error changing from 1600 to 0000.

[sydney-runkle]

Wonderful, thanks!