Move lint, test deps to dependency-groups

We do not expect people to install these. dependency groups
are designed for this.

Author: stephenfin

pyproject.toml

@@ -34,8 +34,10 @@ requires-python = ">=3.10"
 Homepage = "https://github.com/testing-cabal/testtools"
 
 [project.optional-dependencies]
-test = ["testscenarios", "testresources"]
 twisted = ["Twisted", "fixtures"]
+
+[dependency-groups]
+test = ["testscenarios", "testresources"]
 dev = [
     "ruff==0.15.2",
     "mypy>=1.0.0",