Fix bug where `-` was passing as a valid date.

[sydney-runkle]

Fix https://github.com/pydantic/pydantic/issues/7872

- is no longer parsing as a valid date.

[codecov[bot]]

Codecov Report

Merging #51 (1223c4d) into main (fd0c948) will decrease coverage by 0.32%. The diff coverage is 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #51 +/- ## ========================================== - Coverage 99.10% 98.78% -0.32% ========================================== Files 6 6 Lines 890 903 +13 ========================================== + Hits 882 892 +10 - Misses 8 11 +3 ``` | [Files](https://app.codecov.io/gh/pydantic/speedate/pull/51?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pydantic) | Coverage Δ | | |---|---|---| | [src/date.rs](https://app.codecov.io/gh/pydantic/speedate/pull/51?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pydantic#diff-c3JjL2RhdGUucnM=) | `100.00% <100.00%> (ø)` | | | [src/numbers.rs](https://app.codecov.io/gh/pydantic/speedate/pull/51?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pydantic#diff-c3JjL251bWJlcnMucnM=) | `95.45% <100.00%> (-3.28%)` | :arrow_down: | ... and [2 files with indirect coverage changes](https://app.codecov.io/gh/pydantic/speedate/pull/51/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pydantic) ------ [Continue to review full report in Codecov by Sentry](https://app.codecov.io/gh/pydantic/speedate/pull/51?src=pr&el=continue&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pydantic). > **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pydantic) > `Δ = absolute (impact)`, `ø = not affected`, `? = missing data` > Powered by [Codecov](https://app.codecov.io/gh/pydantic/speedate/pull/51?src=pr&el=footer&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pydantic). Last update [fd0c948...1223c4d](https://app.codecov.io/gh/pydantic/speedate/pull/51?src=pr&el=lastupdated&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pydantic). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pydantic).

[samuelcolvin]

replaced by #52.