Update gradio requirement from ~=5.12 to ~=5.13 in /requirements

Updates the requirements on [gradio](https://github.com/gradio-app/gradio) to permit the latest version.
- [Release notes](https://github.com/gradio-app/gradio/releases)
- [Changelog](https://github.com/gradio-app/gradio/blob/main/CHANGELOG.md)
- [Commits](https://github.com/gradio-app/gradio/compare/[email protected]@5.13.1)

---
updated-dependencies:
- dependency-name: gradio
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

requirements/requirements.txt

@@ -1,5 +1,5 @@
 ovos-plugin-manager>=0.0.25,<1.0.0
 fastapi~=0.115
 uvicorn~=0.34
-gradio~=5.12
+gradio~=5.13
 ovos-utils>=0.0.38,<1.0.0