Bump to pydantic 2.8.0 (#702)

* deps: bump pydantic from 1.10.15 to 2.8.0

Bumps [pydantic](https://github.com/pydantic/pydantic) from 1.10.15 to 2.8.0.
- [Release notes](https://github.com/pydantic/pydantic/releases)
- [Changelog](https://github.com/pydantic/pydantic/blob/main/HISTORY.md)
- [Commits](https://github.com/pydantic/pydantic/compare/v1.10.15...v2.8.0)

---
updated-dependencies:
- dependency-name: pydantic
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

* Update dependencies
run the bump-pydantic tool.

* Migrate the validate_uuid using field_validator.

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

src/healthchecks_io/client/sync_client.py

@@ -302,6 +302,7 @@ class Client(AbstractClient):
 
         svg, json, shields: reports two states: "up" and "down". It considers any checks in the grace period
             as still "up".
+
         svg3, json3, shields3: reports three states: "up", "late", and "down".
 
         The response includes a special * entry: this pseudo-tag reports the overal status