Update gdsfactory requirement from ~=8.4.0 to >=8.4,<9.1

Updates the requirements on [gdsfactory](https://github.com/gdsfactory/gdsfactory) to permit the latest version.
- [Release notes](https://github.com/gdsfactory/gdsfactory/releases)
- [Changelog](https://github.com/gdsfactory/gdsfactory/blob/main/CHANGELOG.md)
- [Commits](gdsfactory/gdsfactory@v8.4.0...v9.0.1)

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

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

pyproject.toml

@@ -12,7 +12,7 @@ classifiers = [
   "Operating System :: OS Independent"
 ]
 dependencies = [
-  "gdsfactory~=8.4.0"
+  "gdsfactory>=8.4,<9.1"
 ]
 description = "gdsfactory VTT PDK"
 keywords = ["python"]