Bump pydantic from 2.3.0 to 2.6.4

Bumps [pydantic](https://github.com/pydantic/pydantic) from 2.3.0 to 2.6.4.
- [Release notes](https://github.com/pydantic/pydantic/releases)
- [Changelog](https://github.com/pydantic/pydantic/blob/main/HISTORY.md)
- [Commits](pydantic/pydantic@v2.3.0...v2.6.4)

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

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

requirements.txt

@@ -6,7 +6,7 @@ h11==0.14.0
 idna==3.4
 isodate==0.6.1
 lxml==4.9.3
-pydantic==2.3.0
+pydantic==2.6.4
 pydantic_core==2.6.3
 pyparsing==3.1.1
 rdflib==7.0.0