deps: update mcp requirement in /authplane-mcp in the pip-all group

Updates the requirements on [mcp](https://github.com/modelcontextprotocol/python-sdk) to permit the latest version.

Updates `mcp` to 1.28.0
- [Release notes](https://github.com/modelcontextprotocol/python-sdk/releases)
- [Changelog](https://github.com/modelcontextprotocol/python-sdk/blob/main/RELEASE.md)
- [Commits](modelcontextprotocol/python-sdk@v1.23.0...v1.28.0)

---
updated-dependencies:
- dependency-name: mcp
  dependency-version: 1.28.0
  dependency-type: direct:production
  dependency-group: pip-all
...

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

Author: dependabot[bot]

authplane-mcp/pyproject.toml

@@ -28,7 +28,7 @@ dependencies = [
     "authplane-sdk",
     # mcp 1.23–1.27 use camelCase `elicitationId`; main has reverted
     # to snake_case, so 1.28+ will likely require an adapter update.
-    "mcp>=1.23.0,<1.28.0",
+    "mcp>=1.23.0,<1.29.0",
     "pydantic>=2.0",
 ]