Bump trame-server from 2.9.0 to 2.9.1 (pyvista#4034)

Bumps [trame-server](https://github.com/Kitware/trame-server) from 2.9.0 to 2.9.1.
- [Release notes](https://github.com/Kitware/trame-server/releases)
- [Changelog](https://github.com/Kitware/trame-server/blob/master/CHANGELOG.md)
- [Commits](Kitware/trame-server@v2.9.0...v2.9.1)

---
updated-dependencies:
- dependency-name: trame-server
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

requirements_docs.txt

@@ -33,7 +33,7 @@ sphinxcontrib-websupport==1.2.4
 sympy==1.11.1
 trame==2.3.2
 trame-client==2.7.0
-trame-server==2.9.0
+trame-server==2.9.1
 trame-vtk==2.0.17
 trimesh==3.20.0
 typed-ast==1.5.4