chore(deps): update swagger-plugin-for-sphinx requirement

Updates the requirements on [swagger-plugin-for-sphinx](https://github.com/SAP/swagger-plugin-for-sphinx) to permit the latest version.
- [Release notes](https://github.com/SAP/swagger-plugin-for-sphinx/releases)
- [Changelog](https://github.com/SAP/swagger-plugin-for-sphinx/blob/main/CHANGELOG.md)
- [Commits](SAP/swagger-plugin-for-sphinx@v5.2.0...v6.0.0)

---
updated-dependencies:
- dependency-name: swagger-plugin-for-sphinx
  dependency-version: 6.0.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

pyproject.toml

@@ -183,7 +183,7 @@ dev = [
     "sphinx_selective_exclude>=1.0.3,<2",
     "sphinx-toolbox>=3.9.0,<4",
     "sphinxext.opengraph>=0.9.1,<1",
-    "swagger-plugin-for-sphinx>=5.2.0,<6",
+    "swagger-plugin-for-sphinx>=5.2.0,<7",
     "tomli>=2.3.0,<3",
     "types-pyyaml>=6.0.12.20250915,<7",
     "types-requests>=2.32.4.20250913,<3",